Preventing allergic contact rashes is simple and can be summed up in one word: avoidance. In other words, you must do everything to limit further exposure. This is all the more important because inadvertent reexposure may trigger a more intense reaction and symptoms than the previous episode.

Sometimes you are able to get around your problem by simply switching to another cosmetic in the same category. For example, let's say you find yourself allergic to a particular brand of red blusher. First, you must stop using the blusher immediately and wait for the rash to clear completely. Next, you should choose another brand of red blusher and use it for three straight days. If you do not develop any problems, it is likely that you were allergic to some other ingredient in the blusher and not the pigment itself. You can then continue using the new product.

On the other hand, should you develop problems with the new red blusher, the red pigment may in fact be the culprit. In that case, once again let the allergy clear completely and then switch to a different color. If you do not develop any problems, the color was probably the allergen, and you must avoid that particular color blusher thereafter.

Should you once again develop allergic symptoms, however, the problem is most likely one or more of the many other ingredients that go into the cosmetic's manufacture. These include solvents, emollients, emulsifying agents (surfactants), preservatives, emulsion stabilizers, thickening and stiffening agents, chemical stabilizers, and antioxidants. And despite manufacturers' claims to the contrary, cosmetic formulations in the same category (that is, all blushers or all foundations) often share many of the same basic ingredients, which means that simply switching to another facial foundation may not solve your problem and may make trial-and-error testing a long, expensive, and frustrating ordeal. When this happens, you would be advised to consult a dermatologist about patch testing to specific ingredients, as described above.