The oral cavity is constantly exposed to a large number of potentially irritating and sensitizing substances. About 10 – 15 different metals, as well as synthetic resin, and other dental materials may act on the buccal mucosa during routine dental treatment. The clinical manifestations of contact hypersensitivity in the mouth vary from subjective difficulties such as pain, burning and dryness of the mucosa to reddish, erosions, ulcers and edematous mucose. These chronic changes are most often associated with long-term exposure of the oral mucosa to dental metals, acrylates, composite materials and other substances. The types of allergic reactions are early or anaphylactoid type and allergic reactions of the delayed or late type. Some clinical examples of early reaction is urticaria, Quincke’s edema and local or generalized anaphylaxis. Late type of allergy is most comon in dental treatement. The localization and distribution of the clinical features often help in the diagnosis, since the patient rarely ever recognizes the connection of his disorder with a specific allergen. Patch test is the best routine examination method to test allergens. Treatement of dental allergy is based on remove allergen materials from oral cavity and replace it with other dental material.