The epicutaneous patch testing is regarded as the best method of diagnosis for allergic contact dermatitis
(ACD). Patch tests can be used to confirm a suspected allergic contact dermatitis and either to recommend avoidance of
particular products or to recommend alternative products in a particular patient. It is based upon re-exposing the skin of
the patient to suspected allergens under controlled conditions. Different test sites and test tapes can be used and different
variables such as intrinsic penetration capacity, concentration, exposure time and vehicle can be changed to obtain an optimal
bioavailability of the haptens. The ideal patch test should cause as few adverse reactions as possible, and be reproducible
and specific. In this paper, the application fields, the advantages and the disadvantages of the patch tests are reviewed.
Other diagnostic methods as the open test, the provocative test, the repeated open application test and the photopatch
test are also discussed.