What signifies a positive response to a patch test?

A positive response to a patch test indicates that the skin has reacted adversely to a substance being tested. This reaction typically manifests as redness, swelling, or irritation, which signifies sensitivity or an allergic response to that particular ingredient. Therefore, the absence of any redness, swelling, or irritation indicates that the tested substance is likely safe for use on the individual’s skin. This means that the skin has tolerated the substance without any signs of adverse reaction, confirming it as a negative or non-reactive result.

In contrast, the other options describe various levels of irritation or sensitivity which would indicate a positive reaction. Mild redness and swelling suggest that the skin is responding to the substance, signaling potential irritation. Itching at the test site can indicate an allergic response as well, while severe irritation would certainly confirm an adverse reaction. Thus, the absence of these symptoms is what defines a successful and safe patch test outcome.