Aquagenic urticaria

Aquagenic urticaria, also known as water allergy or water urticaria, is a rare physical form of urticaria. This condition is characterized by an itchy skin reaction upon contact with water, regardless of its temperature. Although sometimes referred to as an allergy, it does not involve a histamine-releasing allergic reaction like other forms of urticaria. Importantly, this response seems to be independent of the water's temperature or any dissolved chemicals, as it can also occur with distilled water and medical saline.

Clinical Manifestations

Aquagenic urticaria presents with symptoms similar to those of other types of physical hives. This includes wheals or small raised hives, intense itching, and skin flushing, especially in areas exposed to water. These symptoms can appear within minutes following water contact. The hives, or urticaria, associated with this condition are typically small (1–3 mm), red or skin-colored welts (wheals) with defined edges. The rash predominantly affects the neck, upper trunk, and arms, but can occur anywhere on the body. Upon removal of the water source, the rash typically subsides within 30 to 60 minutes..

Etiology

The exact etiology of aquagenic urticaria remains unclear. Current hypotheses suggest that the immune response may be triggered by tiny quantities of an unknown substance in the water, or by the water interacting with a substance on or within the skin. Although it is often referred to as a water allergy, this is a misnomer, as this condition does not represent a true allergy to water, particularly given the large proportion of water in the human body.

Diagnosis

Diagnosis of aquagenic urticaria typically commences with an evaluation of the patient's medical history to identify any potential triggers for the observed symptoms. This is often followed by a water challenge test, in which water is applied to the upper body for a duration of 30 minutes. The water may be applied directly or a water-soaked paper towel may be used. The test often involves distilled water, tap water, and saline to investigate any differences in the reaction. Following removal of the water, the skin is observed for a reaction for the next 10–15 minutes.

Given that aquagenic urticaria frequently coexists with other forms of physical urticaria, additional tests may be conducted to check for these conditions. An ice cube may be placed on the forearm to test for cold urticaria, while exposure to a hot bath may be used to test for cholinergic urticaria. Furthermore, lesions, if present, will be inspected to identify potential underlying causes of their appearance.

Aquagenic urticaria Resources
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