Allergic contact dermatitis (ACD) describes a delayed type of hypersensitivity reaction that occurs when the skin comes into contact with a chemical to which it has previously been sensitized. A major development in ACD diagnosis was the creation of the patch test, which is credited to Josef Jadassohn1 and was first described as a method to understand mercury-induced eczematous dermatitis in a syphilis patient. Patch testing involves applying patches containing various allergens on the upper back of an individual, removing the patches, then interpreting the skin’s reaction to the allergens. While it is a brilliant technique, interpretation of the test results is yet to be perfected. Following are some aspects of this technique that require consideration, including the ingredients used, related legislative measures and testing limitations.