Allergic contact dermatitis (ACD) affects millions of people worldwide. In an attempt to decrease the incidence of contact dermatitis, several countries have implemented legislations to reduce the population's exposure to known sensitizers. To determine whether these legislations have been effective, we reviewed several studies examining trends in patch test reactivity before and after implementation of these legislations. Common sensitizers studied include nickel, gluceryl monothioglycolate fragrances, chromate, and thiuram. Overall, the evidence suggests a decreasing trend of ACD with appropriate formulation changes, however some of the data may be confounded by biases, and additionally, exposure to the sensitizer may still exist via non-compliance to regulations by small manufacturers. In the future population based studies should be conducted to more accurately assess trends in ACD. (C) 2003 Elsevier Science Ltd. All rights reserved.