Allergy

This article deals specifically with IgE-mediated hypersensitivity. For other types of allergic or hypersensitive reactions see the main article: Hypersensitivity

An allergy can refer to several kinds of immune reactions including Type I hypersensitivity in which a person's body is hypersensitised and develops IgE type antibodies to typical proteins. When a person is hypersensitised, these substances are known as allergens. The word allergy derives from the Greek words allos meaning "other" and ergon meaning "work". Type I hypersensitivity is characterised by excessive activation of mast cells and basophils by immunoglobulin E resulting in a systemic inflammatory response that can result in symptoms as benign as a runny nose, to life-threatening anaphylactic shock and death.

Allergy is a very common disorder and more than 50 million Americans suffer from allergic diseases. Allergies are the 6th leading cause of chronic disease in the United States, costing the health care system $18 billion annually (Allergy statistics).

History

The term and concept of "allergy" was coined by a Viennese pediatrician named Clemens von Pirquet in 1906 [1]. He observed that the symptoms of some of his patients might have been a response to outside allergens such as dust, pollen, or certain foods. For a long time all hypersensitivities were thought to stem from the improper action of inflammatory immunoglobulin class IgE, however it soon became clear that several different mechanisms utilizing different effector molecules were responsible for the myriad of disorders previously classified as "allergies". A new four-class (now five) classification scheme was designed by P. G. H. Gell and R. R. A. Coombs. Allergy has since been kept as the name for Type I Hypersensitivity, characterised by classical IgE mediation of effects.

Signs and symptoms

Allergy is characterised by a local or systemic inflammatory response to allergens. Local symptoms are:

• Nose: swelling of the nasal mucosa (allergic rhinitis)
• The distinctive behavior known as nasal salute, also known as allergy salute, is the habit of wiping of the nose in an upward direction due to itching.
• Eyes: redness and itching of the conjunctiva (allergic conjunctivitis)
• Airways: bronchoconstriction, wheezing and dyspnoea, sometimes outright attacks of asthma
• Ears: feeling of fullness, possibly pain, and impaired hearing due to the lack of eustachian tube drainage.
• Skin: various rashes, such as eczema, hives (urticaria) and contact dermatitis.

Hives are a common allergic symptom

Systemic allergic response is also called anaphylaxis. Depending of the rate of severity, it can cause cutaneous reactions, bronchoconstriction, edema, hypotension, coma and even death.

Hay fever is one example of an exceedingly common minor allergy - large percentages of the population suffer from hayfever symptoms in response to airborne pollen. Asthmatics are often allergic to dust mites. Apart from ambient allergens, allergic reactions can be due to medications.

Diagnosis

There are several methods for the diagnosis and assessment of allergies.

Skin test

The typical and most simple method of diagnosis and monitoring of Type I Hypersensitivity is by skin testing, also known as prick testing due to the series of pricks made into the patient's skin. Small amounts of suspected allergens and/or their extracts (pollen, grass, mite proteins, peanut extract, etc.) are introduced to sites on the skin marked with pen or dye (the ink/dye should be carefully selected, lest it cause an allergic response itself). The allergens are either injected intradermally or into small scratchings made into the patient's skin, often with a lancet. Common areas for testing include the inside forearm and back. If the patient is allergic to the substance, then a visible inflammatory reaction will usually occur within 30 minutes. This response will range from slight reddening of the skin to full-blown hives in extremely sensitive patients.

After performing the skin test and receiving results, the doctor may apply a steroid cream to the test area to reduce discomfort (such as itching and inflammation).

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  Allergy skin testing

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  Skintest2

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  Epikutanni-test

Problems with skin test

While the skin test is probably the most preferred means of testing because of its simplicity and economics, it is not without complications. Some people may display a delayed-type hypersensitivity (DTH) reaction which can occur as far as 6 hours after application of the allergen and last up to 24 hours. This can also cause serious long-lasting tissue damage to the affected area. Fortunately, these types of serious reactions are quite rare.

Additionally, the application of previously unencountered allergens can actually sensitize certain individuals to the allergen, causing the inception of a new allergy in susceptible individuals.

Skins tests also are not always able to pinpoint a patient's specific allergies if the patient has an allergy but does not react to the skin test allergen.

Total IgE count

Another method used to qualify type I hypersensitivity is measuring the amount of serum IgE contained within the patient's serum. This can be determined through the use of radiometric and colormetric immunoassays. Even the levels the amount of IgE specific to certain allergens can be measured through use of the radioallergosorbent test (RAST).

Allergy testing machine

Treatment

There are limited mainstream medical treatments for allergies. Probably the most important factor in rehabilitation is the removal of sources of allergens from the home environment, and avoiding environments in which contact with allergens is likely.

Immunotherapy

Hyposensitization is a form of immunotherapy where the patient is gradually vaccinated against progressively larger doses of the allergen in question. This can either reduce the severity or eliminate hypersensitivity altogether. It relies on the progressive skewing of IgG ("the blocking antibody") production, as opposed to the excessive IgE production seen in hypersensitivity type I cases.

In the 1960s, Dr. Len McEwen in the United Kingdom developed a treatment for allergies known as enzyme potentiated desensitization, or EPD. EPD uses much lower doses of antigens than conventional treatment, with the addition of an enzyme. EPD is available in the United Kingdom and Canada, and was available in the United States until 2001, when the Food and Drug Administration revoked its approval for an investigative study being performed. Since that time an American counterpart to EPD, known as Low Dose Antigens, or LDA, has been formulated from components approved by the FDA, and is available for treatment from a small number of doctors in the United States. EPD (and LDA) is still considered experimental by many mainstream doctors and medical insurance companies, and many doubt that it is more effective than a placebo.

A third form of immunotherapy involves the intravenous injection of monoclonal anti-IgE antibodies. These bind to free and B-cell IgE signalling such sources for destruction. They do not bind to IgE already bound to the Fc receptor on basophils and mast cells as this would stimulate the allergic inflammatory response.

Chemotherapy

Several antagonistic drugs are used to block the action of allergic mediators, preventing activation of cells and degranulation processes. They include antihistamines, cortisone, epinephrine (adrenalin), theophylline and Cromolyn sodium. These drugs help alleviate the symptoms of allergy but play little role in chronic alleviation of the disorder. They can play an imperative role in the acute recovery of someone suffering from anaphylaxis (which is why those allergic to bee stings, peanuts, nuts, and shellfish often carry an adrenalin needle with them at all times).

Alternative therapies

In alternative medicine, a number of treatment modalities are considered effective by its practitioners in the treatment of allergies, particularly herbal medicine, homeopathy, traditional Chinese medicine and kinesiology. However, these claims lack well-established evidence. Treatment or management of allergies with alternative therapies is generally criticised by mainstream medical pratitioners and researchers to be supported only by anecdotes.

Pathophysiology

All hypersensitivities result from an aberration somewhere in the normal immune process. The exact cause of such malfunctions is not always apparent, however, and several arguments from genetic-basis, environmental-basis and intermediate proponents exist with varying validity and acceptance.

Acute response

The difference between a type I hypersensitivity reaction against an allergen to the normal humoral response against a foreign body is that plasma cells secrete IgE as opposed to either IgM (against novel antigens) or IgG (against immunized antigens). IgE binds to Fc receptors on the surface of mast cells and basophils, both involved in the acute inflammatory response.

When IgE is first secreted it binds to the Fc receptors on a mast cell or basophil, and such a IgE-coated cell is said to be sensitized to the allergen in question. A later exposure by the same allergen causes reactivation of these IgE, which then signals for the degranulation of the sensitized mast cell or basophil. There is now strong evidence that mast cells and basophils require costimulatory signals for degranulation in vivo, derived from GPCRs such as chemokine receptors. These granules release histamine and other inflammatory chemical mediators (cytokines, interleukins, leukotrienes, and prostaglandins) into the surrounding tissue causing several systemic effects, such as vasodilation, mucous secretion, nerve stimulation and smooth muscle contraction. This results in the previously described symptoms of rhinorrhea, itchiness, dyspnea, and anaphylaxis. Depending on the individual, allergen, and mode of introduction, the symptoms can be system-wide (calliscal anaphylaxis), or localised to particular body systems (for example, asthma to the respiratory system; eczema to the dermis).

Late-phase response

After the chemical mediators of the acute response subside, late phase responses can often occur. This is due to the migration of other leukocytes such as neutrophils, lymphocytes, eosinophils and macrophages to the initial site. The reaction is usually seen 4-6 hours after the original reaction and can last from 1-2 days. Cytokines from mast cells may also play a role in the persitence of long-term effects. Late phase responses seen in asthma are slightly different to those seen in other allergic responses.

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  The Allergy Pathway

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  Tissues Affected In Allergic Inflammation

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  Allergy Degranulation processes 1 - antigen; 2 - IgE antibody; 3 - FcεRI receptor; 4 - preformed mediators (histamine, proteases, chemokines, heparine); 5 - granules; 6 - mast cell; 7 - newly formed mediators (prostaglandins, leukotrienes, thromboxanes, PAF)

Basis of the allergic response

Genetic basis

There is much evidence to support the genetic basis of allergy, as allergic parents are more likely to have allergic children, and their allergies are likely to be stronger than those from non-allergic parents. However some allergies are not consistent along genealogies with parents being allergic to peanuts, but having children allergic to ragweed, or siblings not sharing the same allergens. Ethnicity has also been shown to play a role in some allergies. Interestingly, in regard to asthma, it has been suggested that different genetic loci are responsible for asthma in people of Caucasian, Hispanic, Asian, and African origins. It has also been suggested that there are both general atopy genes and tissue-specific allergy genes that target the allergic response to specific mucosal tissues. Potential disease associated alleles include both coding region variation and SNPs found in gene regulatory elements.

Relationship with parasites

Some recent research has also begun to show that some kinds of common parasites, such as intestinal worms (e.g. hookworms), secrete immunosuppressant chemicals into the gut wall and hence the bloodstream which prevent the body from attacking the parasite. This gives rise to a new slant on the "hygiene hypothesis" - that co-evolution of man and parasites has in the past led to an immune system that only functions correctly in the presence of the parasites. Without them, the immune system becomes unbalanced and oversensitive. Gutworms and similar parasites are present in untreated drinking water in undeveloped countries, and in developed countries until the routine chlorination and purification of drinking water supplies. This also coincides with the time period in which a significant rise in allergies has been observed. So far, there is only sporadic evidence to support this hypothesis - one scientist who suffered from seasonal allergic rhinitis (hayfever) infected himself with gutworms and was immediately 'cured' of his allergy with no other ill effects. Full clinical trials have yet to be performed however. It may be that the term 'parasite' could turn out to be inappropriate, and in fact a hitherto unsuspected symbiosis is at work.

Basis of increasing prevalence

There has been a notable increase in the commonness of allergies in the past decades, and there are multiple hypotheses explaining this phenomenon. This is in part because we know what they are, in contrast to earlier humans who would think that it is a non-important illness.

The Hygiene Hypothesis

One theory that has been gaining strength is the "hygiene hypothesis". This theory maintains that since children in more affluent countries are leading a cleaner and cleaner life (less exposure to dirt, extra use of disinfectants, etc), their immune systems have less exposure to parasites and other pathogens than children in other countries or in decades past. Their immune systems may, therefore, have many "loaded guns", cells which might have targeted, say, the intestinal worms that no longer cause trouble in affluent neighbourhoods. Having no reasonable target, these cells inadvertently become activated by environmental antigens that might only cause minor reactions in others. It is the symptoms of this exaggerated response that is seen as the allergic reaction.

Many common allergies such as asthma have seen huge increases in the years since the second world war, and many studies appear to show a correlation between this and the increasingly affluent and clean lifestyles in the West. This is supported by studies in less developed countries that do not enjoy western levels of cleanliness, and similarly do not show western levels of incidences of asthma and other allergies. During this same period, air quality, at one time considered the "obvious" cause of asthma, has shown a considerable improvement. This has led some researchers to conclude that it is our "too clean" upbringing that is to blame for the lack of immune system stimulation in early childhood.

So far the evidence to support this theory is limited. One supporting fact is that many Chinese will develop hay fever after moving into USA for three or more years. However, contradictory examples also exist.

Increasing use of chemicals

Another theory is the exponential use and abuse of chemicals in affluent nations since the second world war. Vast numbers of chemicals are introduced into our indoor and outdoor environments with little or no testing regarding their toxicity to living beings. Many believe that air quality is getting worse rather than better, particularly if one considers indoor air quality as well as outdoor. (Indoor air quality has become significantly worse since building codes changed in the 1970s to make buildings more air-tight to conserve energy. This affects buildings built since that time.) Adverse reactions to toxins vary considerably from one person to another, and can involve extremes in symptoms including the neurological and endocrine systems as well as the more commonly recognized allergy symptoms listed above.

In 2004, a joint Swedish-Danish research team (Bornehag et al.) found a very strong link between allergies in children and the phthalates DEHP and BBzP, commonly used in PVC.

Allergies are also viewed by some medical practitioners as a negative consequence of the use and abuse of antibiotics and vaccinations. This mainstream Western approach to treatment and prevention of infectious disease has been used in the more affluent world for a longer period of time than in the rest of the world, hence the much greater commonality of allergies there. It is hypothesized that use of antibiotics and vaccination affect the immune system, and that allergies are a dysfunctional immune response. There is, however, very little evidence to support this view.

Common allergens

Misc. pollen colorized

House dust mite

In addition to foreign proteins found in foreign serum (from blood transfusions) and vaccines, common allergens include:

• Plant pollens (Hay fever)
  • rye grass
  • ragweed
  • timothy grass
  • birch trees
• Mold spores
• Drugs
  • penicillins
  • sulfonamides
  • salicylates (also found naturally in numerous fruits)
  • local anaesthetics
• Foods (food allergy)
  • nuts
  • sesame
  • seafood
  • egg (typically albumen, the white)
  • peas, beans, peanuts, soybeans and other legumes
  • soy
  • milk
  • wheat
  • corn or maize
• Insect stings
  • bee sting venom
  • wasp sting venom
• Animal products (animal allergy)
  • Animal hair and dander
  • cockroach calyx
  • dust mite excretion

Glossary

• 5-Oxo-eicosatetraenoic acid - A potent eosinophilic chemotactic factor involved in allergic reactions, playing a role in the pathophysiology of asthma and other allergic diseases.
• ALCAT test - A controversial test that claims to identify food sensitivities associated with inflammation and chronic health conditions, though its clinical validity and utility in allergology are debated.
• Aeroallergen - Any airborne substance, such as pollen, dust mites, or mold spores, that can trigger allergic reactions in susceptible individuals.
• Allergen immunotherapy - A long-term treatment approach for allergic diseases which involves gradually increasing doses of the allergen, aiming to desensitize the immune system and reduce allergic responses.
• Allergen of the Year - An annual designation by the American Contact Dermatitis Society for a specific allergen that has significant clinical relevance in contact dermatitis.
• Allergen - A typically harmless substance that can trigger an immune response leading to an allergic reaction in predisposed individuals, such as pollen, food proteins, or pet dander.
• Allergic conjunctivitis - Inflammation of the conjunctiva of the eyes caused by allergic reactions to substances like pollen or pet dander, characterized by itching, redness, and tearing.
• Allergic inflammation - The immune system's response to allergens, leading to symptoms such as swelling, redness, and itchiness in affected tissues.
• Allergic reactions to anesthesia - Adverse responses to anesthetic agents, ranging from mild allergic skin reactions to severe, life-threatening anaphylaxis.
• Allergic response - The body's immune reaction to an allergen, which can manifest as various symptoms including sneezing, itching, hives, and in severe cases, anaphylaxis.
• Allergic rhinitis - A common allergic condition characterized by symptoms such as sneezing, itching, nasal congestion, and runny nose, often triggered by airborne allergens.
• Allergic salute - A habitual gesture, often seen in children with allergic rhinitis, where the hand is used to rub or wipe the nose upwards to relieve itchiness and congestion.
• Allergic transfusion reaction - An adverse reaction to blood transfusion, caused by an immune response to donor blood components, leading to symptoms ranging from mild to severe, including anaphylaxis.
• Allergies in children - The occurrence and management of allergic conditions in pediatric populations, including food allergies, atopic dermatitis, and allergic rhinitis.
• Allergist - A medical specialist who diagnoses and treats allergic diseases, employing various methods including allergy testing, allergen avoidance, medication, and immunotherapy.
• Allergy test - Diagnostic procedures used to identify specific allergens responsible for an individual's allergic reactions, including skin prick tests, blood tests, and challenge tests.
• Allergy to cats - An allergic reaction to proteins found in cat skin cells, saliva, and urine, leading to symptoms such as sneezing, itching, and asthma in sensitized individuals.
• Allergy - A condition in which the immune system reacts abnormally to a foreign substance, causing symptoms that can range from mild to life-threatening.
• Alpha-gal syndrome - An allergic reaction to red meat and other products made from mammals, caused by a sugar molecule called alpha-gal, which can lead to symptoms ranging from hives to anaphylaxis.
• American Academy of Allergy, Asthma, and Immunology - A professional organization dedicated to the advancement of knowledge and practice in the field of allergy, asthma, and immunology.
• Anaphylaxis Campaign - A UK-based charity focused on raising awareness of anaphylaxis, a severe and potentially life-threatening allergic reaction, and supporting those at risk.
• Anaphylaxis - A severe, potentially life-threatening allergic reaction that can occur rapidly and affect multiple body systems, requiring immediate medical attention.
• Animal allergy - Allergic reactions to proteins found in the skin, saliva, or urine of animals, causing symptoms such as sneezing, itching, and asthma in sensitized individuals.
• Anti–Saccharomyces cerevisiae antibody - Antibodies against the yeast Saccharomyces cerevisiae, which are associated with certain autoimmune diseases, including Crohn's disease.
• Aquagenic urticaria - A rare form of physical urticaria triggered by contact with water, leading to the development of hives on the skin.
• Ara h1 - A major allergen protein found in peanuts that can cause allergic reactions in susceptible individuals, often involved in severe food allergy cases including anaphylaxis.
• Aspirin-exacerbated respiratory disease - A condition characterized by asthma, nasal polyps, and respiratory reactions to aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs).
• Asthma and Allergy Foundation of America - A leading nonprofit organization dedicated to improving the quality of life for people with asthma and allergic diseases through education, advocacy, and research.
• Asthma and Allergy Friendly - A certification program that identifies products and services that are suitable for people with asthma and allergies, helping to reduce exposure to potential allergens.
• Balsam of Peru - A natural resin used in various products that can cause allergic contact dermatitis in sensitive individuals due to its fragrance and chemical components.
• Beef allergy - An adverse immune response to proteins found in beef, which can range from mild allergic reactions to severe cases of alpha-gal syndrome.
• Bernadette Eberlein - A notable researcher and clinician in the field of dermatology and allergology, recognized for her contributions to understanding contact dermatitis and other allergic conditions.
• Bet v I allergen - The primary allergen found in birch pollen, known for causing allergic reactions in susceptible individuals, including respiratory symptoms and oral allergy syndrome.
• Betamethasone/dexchlorpheniramine - A combination medication used to treat allergic conditions by reducing inflammation and suppressing allergic responses.
• Botanical sexism - A concept referring to the preference for planting male plants in urban landscapes, which can increase pollen production and exacerbate allergic reactions in the population.
• Buehler test - A skin sensitization test used in dermatological research to identify potential allergens by repeated application of a substance to the skin of a test subject.
• Can f 1 - A major dog allergen found in canine saliva and dander, responsible for triggering allergic reactions in individuals with dog allergies.
• Cherrybrook Kitchen - A brand known for producing allergen-free baking mixes, catering to individuals with food allergies and intolerances.
• Cladosporium - A common mold found in the environment that can act as an aeroallergen, causing respiratory allergies and symptoms in sensitized individuals.
• Cold sensitivity - A condition where exposure to cold temperatures triggers allergic or hypersensitivity reactions, including cold urticaria and anaphylaxis in severe cases.
• Contact dermatitis - An allergic or irritant skin reaction resulting from direct contact with an allergen or irritant substance, leading to redness, itching, and blistering.
• Corn allergy - An adverse immune response to proteins found in corn and corn products, leading to allergic symptoms in affected individuals.
• Cross-reactive carbohydrate determinants - Molecules found in plant and insect proteins that can cause false positive results in allergy tests due to their cross-reactivity with human IgE antibodies.
• Dentin hypersensitivity - A common dental condition characterized by sharp pain in response to stimuli such as cold, heat, or touch, affecting the dentin layer of the teeth.
• Desensitization (medicine) - A process used in allergology and other medical fields to reduce or eliminate allergic reactions by gradually exposing the patient to increasing doses of the allergen.
• Drug allergy - An adverse reaction to a medication that involves the immune system, ranging from mild rashes to severe reactions like anaphylaxis.
• Drug intolerance - A non-immune-mediated adverse reaction to a drug, often characterized by an inability to tolerate the normal dosage of the medication due to side effects.
• Dust mite allergy - An allergic reaction to tiny bugs that commonly live in house dust, causing symptoms such as sneezing, nasal congestion, and itchy eyes in sensitized individuals.
• ECARF Quality Seal - A certification awarded by the European Centre for Allergy Research Foundation to products and services that meet high standards for allergen management, aiming to improve the quality of life for allergy sufferers.
• Egg allergy - An immune response to proteins found in eggs, leading to allergic reactions that can range from mild to severe, including anaphylaxis.
• Elimination diet - A dietary strategy used to identify foods that an individual is allergic or intolerant to by removing potential triggers from the diet and then systematically reintroducing them.
• Eosinophilic myocarditis - A rare form of myocarditis characterized by eosinophilic infiltration of the heart muscle, which can be associated with hypersensitivity reactions, including those to medications.
• European Academy of Allergy and Clinical Immunology - An organization dedicated to promoting research, education, and clinical practice in the field of allergy and clinical immunology across Europe and beyond, aiming to improve patient care and health outcomes related to allergic diseases.
• European Centre for Allergy Research Foundation - A foundation focused on supporting allergy research, public education, and the development of innovative approaches to diagnose, treat, and prevent allergic diseases.
• Exercise-induced anaphylaxis - A rare condition in which physical activity triggers a severe allergic reaction, leading to symptoms such as hives, difficulty breathing, and potentially life-threatening anaphylaxis.
• FITkit - A diagnostic tool used in allergology to measure specific IgE antibodies against multiple allergens simultaneously, aiding in the identification of allergic sensitivities.
• Fish allergy - An adverse immune reaction to proteins found in fish, causing allergic symptoms in affected individuals, ranging from mild reactions to severe anaphylaxis.
• Food allergy - An immune system response to a food protein that the body mistakenly believes is harmful, leading to symptoms such as itching, swelling, gastrointestinal distress, and in severe cases, anaphylaxis.
• Food intolerance - Adverse reactions to food that do not involve the immune system, often due to enzymatic deficiencies or sensitivities to food additives, leading to symptoms like gastrointestinal discomfort.
• Food protein-induced enterocolitis syndrome (FPIES) - A severe, non-IgE-mediated gastrointestinal food allergy that typically occurs in infants and young children, causing vomiting, diarrhea, and dehydration in response to certain foods.
• Fruit allergy - An allergic reaction to proteins found in certain fruits, often related to pollen food syndrome or oral allergy syndrome, leading to itching or swelling in the mouth and throat.
• GWAS in allergy - Genome-Wide Association Studies conducted to identify genetic factors that contribute to allergic diseases, providing insights into the underlying mechanisms of allergies and potential targets for therapy.
• Galactose-alpha-1,3-galactose (alpha-gal) - A sugar molecule found in mammalian meat that can trigger alpha-gal syndrome, a delayed allergic reaction to red meat and other products derived from mammals.
• Garlic allergy - An immune response to garlic, leading to allergic reactions in some individuals, which can range from mild symptoms like skin irritation to more severe reactions including anaphylaxis.
• Guinea pig maximisation test - An in vivo test used to assess the allergenic potential of chemicals by inducing an allergic response in guinea pigs, historically used in the development and safety assessment of cosmetics and pharmaceuticals.
• Hay fever in Japan - Refers to the widespread occurrence of allergic rhinitis in Japan, particularly due to the pollen of Japanese cedar trees, which affects a significant portion of the population each spring.
• Heat intolerance - A condition characterized by an inability to withstand hot temperatures, which can be a symptom of various underlying medical conditions, including allergic and autoimmune diseases.
• Helminthic therapy - The use of parasitic worms in a controlled manner to treat autoimmune diseases and allergies by modulating the immune system, based on the hygiene hypothesis.
• Histamine intolerance - A condition arising from the inability to break down histamine efficiently, leading to symptoms such as headaches, skin irritation, and gastrointestinal distress after consuming histamine-rich foods.
• Histamine liberators - Substances that can trigger the release of histamine from mast cells, potentially exacerbating symptoms in individuals with allergies or histamine intolerance.
• Human maximisation test - A method used in dermatological research to assess the potential of substances to cause skin sensitization and allergic contact dermatitis in humans.
• Hydrodynamic theory (dentistry) - A theory explaining the mechanism of dentin hypersensitivity, suggesting that movement of fluid within the dentinal tubules triggers nerve responses causing pain.
• Hygiene hypothesis - A theory that suggests a lack of early childhood exposure to infectious agents, symbiotic microorganisms, and parasites increases susceptibility to allergic diseases by suppressing the natural development of the immune system.
• Hypersensitivity - An exaggerated or inappropriate immune response to substances that are normally harmless, including allergic reactions and other types of immune responses.
• Hypoallergenic dog breed - Dog breeds that are claimed to be more compatible with allergic individuals by producing fewer allergens, though no dog breed is completely allergen-free.
• Hypoallergenic - Describes products or substances that are unlikely to cause an allergic reaction, often used in the context of cosmetics, textiles, and pet breeds.
• Idiosyncrasy - An unusual or abnormal reaction to substances or drugs that is not due to an allergy, often genetically determined and manifesting as an atypical pharmacological response.
• Insect sting allergy - An allergic reaction to the venom of stinging insects such as bees, wasps, and hornets, which can range from mild local reactions to severe systemic responses, including anaphylaxis.
• La Jolla Institute for Immunology - A leading research institute focused on the study of the immune system, including allergies and asthma, aiming to develop innovative treatments and cures for immune system disorders.
• Laboratory animal allergy - An allergic response experienced by researchers and technicians who work with laboratory animals, triggered by allergens such as dander, urine, or saliva from the animals.
• Latex allergy - An allergic reaction to natural rubber latex, found in many medical and consumer products, leading to symptoms ranging from skin irritation to anaphylaxis.
• List of allergens - A compilation of substances known to cause allergic reactions in susceptible individuals, including food proteins, pollen, dust mites, molds, animal dander, and chemical irritants.
• Local lymph node assay - An in vivo test used to evaluate the allergenic potential of chemicals based on their ability to stimulate lymph node cell proliferation in the exposed animal.
• MELISA - An acronym for Memory Lymphocyte Immunostimulation Assay, a blood test used to detect hypersensitivity to various substances, including metals and chemicals.
• Major urinary proteins - A group of proteins found in the urine of mice and other rodents, which can act as allergens and contribute to laboratory animal allergies.
• Maple bark disease - A respiratory illness caused by inhaling the spores of fungi growing on maple bark, leading to symptoms such as cough, fever, and malaise in exposed individuals.
• Mariana Castells - A prominent figure in the field of allergology and immunology, recognized for her contributions to understanding and treating mast cell disorders and anaphylaxis.
• Meat allergy - An allergic reaction to certain proteins found in meat, which can include alpha-gal syndrome, a delayed reaction to mammalian meat and products.
• Metal allergy - An allergic response to metal ions, such as nickel, chromium, and cobalt, commonly manifesting as allergic contact dermatitis upon skin contact with metal-containing objects.
• Michael Chiarello - May refer to a public figure not directly related to allergology. If referencing contributions to allergology or related fields, specificity is needed regarding the context and relevance.
• Milk allergy - An immune-mediated adverse reaction to one or more proteins found in cow's milk, which can range from mild symptoms to life-threatening anaphylaxis in allergic individuals.
• Mosquito bite allergy - An allergic reaction to the saliva of mosquitoes, resulting in exaggerated swelling, redness, and itching at the site of the bite.
• Mouse ear swelling test - An experimental model used in research to evaluate the allergic and inflammatory responses of the skin to various substances in mice.
• Multiple chemical sensitivity - A condition characterized by adverse reactions to low levels of chemicals in the environment, often with symptoms that overlap with allergies, though the mechanism is not well understood.
• N,N'-Dicyclohexylcarbodiimide - A chemical compound used in organic synthesis that can cause allergic reactions and sensitization in exposed individuals, emphasizing the importance of safety in chemical handling.
• Nasal provocation test - A diagnostic procedure used to determine the nasal airway's response to specific allergens, useful in diagnosing allergic rhinitis and identifying causative allergens.
• Ogren Plant Allergy Scale - A system developed to rate plants based on their potential to produce allergenic pollen, helping individuals with pollen allergies to choose less allergenic plants for landscaping.
• Oral allergy syndrome - A type of food allergy that results in immediate allergic reactions in the mouth and throat upon eating certain fresh fruits, vegetables, and nuts, often linked to pollen allergies.
• Oral food challenge - The gold standard diagnostic test for food allergies, involving the supervised consumption of the suspected allergenic food in gradually increasing amounts to observe for allergic reactions.
• Oral mite anaphylaxis - A rare allergic reaction triggered by the ingestion of mites present in contaminated food, leading to symptoms of anaphylaxis.
• Orthostatic intolerance - A condition characterized by the inability to tolerate changes in body position, such as standing from a seated or lying position, without developing symptoms; while not directly related to allergies, it highlights the complexity of differential diagnoses in symptomatic individuals.
• Para tertiary butylphenol formaldehyde resin - A chemical used in adhesives and footwear, among other products, which can cause allergic contact dermatitis in sensitive individuals.
• Peanut allergy - An immune-mediated reaction to peanut proteins, one of the most common and potentially severe food allergies, which can lead to anaphylaxis in highly sensitive individuals.
• Perfume intolerance - A condition where individuals experience adverse reactions to fragrances, which can include respiratory symptoms, skin irritation, or headaches, not always mediated by an allergic mechanism.
• Platinosis - A form of occupational lung disease and hypersensitivity to platinum salts, leading to symptoms such as asthma, dermatitis, and respiratory irritation in affected workers.
• Pollen - Tiny, powdery grains needed to fertilize many kinds of plants, and a common aeroallergen that can trigger allergic rhinitis, commonly known as hay fever, and other allergic reactions.
• Polyethylene glycol - A polymer used in many pharmaceutical, cosmetic, and industrial applications, which has been implicated in rare cases of allergic reactions, highlighting the importance of allergy awareness in product safety.
• Pool chlorine hypothesis - A hypothesis suggesting that exposure to chlorinated swimming pools may increase the risk of developing respiratory allergies and asthma, based on the irritant properties of chlorine and its by-products.
• Pork allergy - An allergic reaction to proteins found in pork, which can be associated with other conditions such as cat-pork syndrome, where individuals allergic to cat albumin also react to pork.
• Pork–cat syndrome - A rare allergic condition where individuals sensitized to cat albumin also react to pork, due to cross-reactivity between the albumin found in both cats and pigs.
• Poultry allergy - An allergic response to chicken or other poultry meats, less common than other meat allergies but can cause similar symptoms including hives, gastrointestinal distress, and anaphylaxis.
• Prausnitz–Küstner test - An historic test for detecting specific allergens, where serum from an allergic individual is injected into a non-allergic individual, followed by exposure to the allergen. It is no longer commonly used due to safety concerns.
• Pseudoallergy - Reactions that resemble allergies but occur without the immune system's involvement, often triggered by direct activation of mast cells or other mechanisms, such as intolerances to additives in foods and drugs.
• Ragweed - A common cause of seasonal allergic rhinitis, with its pollen being a major aeroallergen in many regions, especially in late summer and early fall.
• Rhinitis - Inflammation of the nasal mucous membranes, which can be allergic or non-allergic in origin, causing symptoms such as sneezing, itching, congestion, and runny nose.
• Rice allergy - An immune response to proteins found in rice, causing allergic reactions in some individuals, including gastrointestinal symptoms, skin rashes, and respiratory distress.
• SEICAP - Sociedad Española de Inmunología Clínica, Alergología y Asma Pediátrica, a Spanish society focused on clinical immunology, allergology, and pediatric asthma, promoting research and education in these areas.
• Salicylate sensitivity - A condition in which individuals react adversely to salicylates, compounds found in various foods, medications, and personal care products, leading to symptoms similar to allergic reactions.
• Sesame allergy - An adverse immune reaction to sesame seeds and products containing sesame, which can cause serious allergic reactions including anaphylaxis in sensitized individuals.
• Shellfish allergy - One of the most common food allergies, characterized by an allergic response to proteins found in shellfish, including shrimp, crab, and lobster, potentially leading to severe reactions.
• Skeeter syndrome - An allergic reaction to mosquito bites, manifesting as excessive swelling, redness, and sometimes fever or infection, more severe than the typical reaction to mosquito bites.
• Skin allergy test - Diagnostic tests, such as the skin prick test or patch test, used to identify substances to which an individual is allergic by observing the skin's reaction to controlled exposure to allergens.
• Slow-reacting substance of anaphylaxis - Historically used term referring to substances released during an allergic reaction that contribute to the symptoms of anaphylaxis, now understood to include leukotrienes and other mediators.
• Soy allergy - An adverse immune response to proteins found in soybeans, one of the common food allergies in children, which can cause a range of symptoms from mild to severe, including anaphylaxis.
• Stallergenes Greer - A global biopharmaceutical company specializing in the development of allergy immunotherapy products, contributing to advancements in the treatment of allergic diseases.
• Stallergenes Greer - A global healthcare company specializing in the diagnosis and treatment of allergies through allergen immunotherapy products and services.
• Sucrose intolerance - A condition in which the body is unable to properly digest sucrose, leading to gastrointestinal symptoms. It differs from a true allergy, as it involves digestive enzyme deficiencies rather than an immune response.
• Sucrose intolerance - A condition where the body is unable to properly digest sucrose, leading to gastrointestinal symptoms after consuming sucrose-containing foods, distinct from an immune-mediated food allergy.
• Sweat allergy - A rare condition where individuals have allergic reactions to components within their own sweat or when sweat interacts with bacteria on the skin, leading to symptoms like itching and hives, particularly during physical activity or heat exposure.
• Torsten Zuberbier - A prominent figure in the field of allergology, known for his extensive research and contributions to understanding the mechanisms and treatment of allergic diseases.
• Toxicodendron orientale - A plant species, similar to poison ivy and poison oak, that contains urushiol, an oil that can cause allergic contact dermatitis upon skin contact with susceptible individuals.
• Toxicodendron radicans - Commonly known as poison ivy, a plant that causes allergic contact dermatitis through exposure to urushiol, leading to itching, blistering, and rash in sensitive individuals.
• Tree nut allergy - An allergic reaction to proteins found in tree nuts, such as almonds, walnuts, and cashews, which can result in symptoms ranging from mild to life-threatening anaphylaxis in sensitized individuals.
• Urushiol-induced contact dermatitis - An allergic reaction caused by contact with urushiol, an oily organic allergen found in plants of the Toxicodendron genus, including poison ivy, poison oak, and poison sumac.
• Wheat allergy - An immune response to proteins found in wheat, leading to allergic reactions that can affect the skin, respiratory system, or gastrointestinal tract in sensitized individuals.
• Wind turbine syndrome - A proposed condition attributed to living near wind turbines, characterized by a range of non-specific symptoms including dizziness, nausea, and sleep disturbance.
• World Allergy Organization - An international umbrella organization whose members consist of regional and national allergology and clinical immunology societies, dedicated to advancing excellence in clinical care, research, education, and training in the field of allergy and clinical immunology worldwide.

See also

• Atopy
• Anaphylaxis
• Multiple chemical sensitivity (MCS).
• Food allergy
• Hypoallergenic
• Hay fever
• Soy allergy
• Systemic reaction

References

• Goldsby RA, Kindt TK, Osborne BA and Kuby J (2003) Immunology, 5th Edition, W.H. Freeman and Company, New York, New York, ISBN 0-7167-4947-5
• Bornehag CG, Sundell J, Weschler CJ, Sigsgaard T, Lundgren B, Hasselgren M, Hagerhed-Engman L. The association between asthma and allergic symptoms in children and phthalates in house dust: a nested case-control study. Environ Health Perspect 2004;112:1393-7. Fulltext. PMID 15471731.
• Ono SJ. Molecular genetics of allergic diseases. Annu Rev Immunol. 2000;18:347-66. Review. PMID 10837062

External links

• American Academy of Allergy, Asthma & Immunology
• Allergy On-Line Journal Club (via JournalReview.org)
• Case Studies in Environmental Medicine (CSEM): Environmental Triggers of Asthma – Agency for Toxic Substances and Disease Registry, U.S. Department of Health and Human Services.

Allergy Resources
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