ABSTRACT
A positive allergic or irritant response from a chemical applied to skin during patch testing requires that the chemical inherently be able to produce the toxicologic response, and that the chemical be absorbed into the skin at a concentration sufficient to produce this response. Various test systems are available with which to apply a chemical to skin. If, for some reason, a test system decreased the absorption of chemical into the skin, then the chances for the chemical to produce a toxicologic response are also reduced. This may result in a false-negative response (Wester and Maibach, 1983). The following is a brief explanation of a patch test, followed by the effect that a patch test system might have on the percutaneous absorption of the test chemical. It is paramount that the test chemical, not the test system, produce the results.
