Patch tests
Keywords: Patch test
What are patch tests?
Patch testing is undertaken for the investigation and confirmation of substances that produce allergic contact dermatitis. It involves applying appropriately diluted allergens to the skin, usually on the back for convenience, for 48 hours. The patch tests are then read at 96 hours as reactions usually take 48–96 hours to develop. Positive reactions produce a patch of dermatitis at the application site of the offending allergen, which will appear as a red and possibly raised, vesicular and even blistering area.
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