If a client shows a positive reaction (redness, itching, swelling) to a patch test, the cosmetologist should:

If a patch (predisposition) test produces a positive reaction — such as redness, itching, burning, or swelling at the test site — the cosmetologist must not perform the haircolor service with that product, because the client is showing a sensitivity or allergy that could cause a serious reaction if the product were fully applied. The service should be declined and the client advised accordingly. Respecting a positive patch test is a critical client-safety rule, and the exam expects candidates to know never to proceed after one.