First, predictive patch testing is a science whose purpose is to test the body's response to various topical products in such a manner that it can predict the likelihood of a given material to be either an irritant or sensitizer under conditions of use. Further, it must accomplish this in a rather short period of time. Finally, it is the science of understanding the body's various response mechanisms in order to characterize the type or lack of reaction, that it is exhibiting.

Given these scientific factors, patch testing is also an art. It is an art requiring years of experience in conducting many RIPT's. It is the ability to look at a reaction or a series of reactions and say that there is something unusual enough about the severity and pattern to be of concern. It is also the ability to look at a similar series of reactions and knowing through experience that this product or ingredient is not likely to be a problem under conditions of use. It is the art of knowing when a rechallenge must be done, when it need not be done or when it is only a recommendation. It is the art of recognizing concentrations that will best predict, not best give zeroes, and of knowing when to change concentrations mid patch and when to just stop patching.

Therefore, the real answer to the question of patch testing as art or science is similar to the breath mint/candy mint question and the answer is also the same — it is both. And, as with all art and science it should never be left to the uninitiated to perform or analyze.