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Patch test
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The patch test is one of the main tests used to work up an allergy, and it has a target of its own: delayed hypersensitivity, the kind mediated by T lymphocytes. Delayed because the reaction does not show up right away.
Here is how it works: a patch carrying the allergen, the suspected substance, is applied to the skin, usually on the back, and left there for forty-eight hours. The allergen stays on the skin until the skin responds. The patch is then removed and the result is read fifteen to sixty minutes later.
It should not be confused with other skin tests. Skin prick testing and intradermal testing measure the immediate response, the one mediated by IgE antibodies. The patch test works along a different pathway: it looks for the type 4 reaction, the one behind allergic contact dermatitis.
In brief
The patch test is one of the main allergy tests, and it evaluates delayed hypersensitivity mediated by T lymphocytes.
A patch containing the allergen is applied to the skin, usually the back, left in place for 48 hours, and read 15 to 60 minutes after removal.
The allergen stays on the skin until the skin responds.
Skin prick and intradermal testing measure the immediate IgE-mediated response; patch testing looks for the type 4 reaction of allergic contact dermatitis.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingAllergy Testing, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingContact Dermatitis, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated