Contact allergy in the mouth: diversity of clinical presentations and diagnosis of common allergens relevant to dental practice.

Delayed-type hypersensitivity reaction or type IV allergic reaction can cause different oral manifestations. They can be localized or diffusely visible on oral mucosa and usually appear 24-72 hours after antigen input. The antigens that cause this type of reaction are mostly external, such as contact allergens (particularly metals) and drugs. It has been shown that the most common oral manifestations are cheilitis, gingivitis, stomatitis, perioral dermatitis, burning mouth syndrome, lichenoid reaction and orofacial granulomatosis. The most important part of diagnosis is the use of patch testing that indicates contact allergic reaction to an allergen. The results of patch testing have shown that the most common proven allergens are gold, nickel, mercury, palladium, cobalt, acrylate, etc. Although connection between specific clinical manifestations and positive patch test results was not always found, patch testing is necessary to prove contact hypersensitivity. Therefore, in patients with oral symptoms, allergic hypersensitivity to dental components has to be considered.