Patch test

Patch test is a method used in dermatology to identify the substances that may have caused an individual to have a contact dermatitis reaction. This test is done by applying a series of small patches, each containing a different substance, to the skin and observing the reaction over a period of time.

Procedure

The patch test procedure involves applying patches with test substances in small chambers or discs to a person's back. The patches are usually left on the skin for 48 hours and must remain dry during this time. After the patches are removed, an initial reading is taken of the reactions. A further reading is taken after another 48 hours to see if further reactions have developed.

Uses

Patch testing is used to identify the cause of allergic contact dermatitis, a type of inflammation of the skin that occurs when the immune system reacts against a substance in contact with the skin. The substances tested are those that are commonly found in the environment and in products that people come into contact with daily.

Risks and complications

While patch testing is generally safe, there are some risks and complications that can occur. These include a strong allergic reaction to one of the test substances, which can cause blistering and scarring. There is also a risk of developing new sensitivities to substances as a result of the test.

See also

• Allergy
• Dermatitis
• Skin test

References

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  Patch test
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  1+ reaction
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  2+ reaction