Variety of materials used in dentistry has the potential to cause irritation or sensitization of tissues within oral cavity or skin to the patient as well as to dental staff. Different metals, synthetic and natural polymers, latex, local anesthetics together with other dental materials can affect oral tissues during dental treatment. Allergic reactions in dental clinic can manifest as early or hypersensitivity type I and delayed or type IV hypersensitivity reactions. Early reactions present with symptoms of warmth, itching, erythema or edema of face and neck, bronchoconstriction and laryngeal edema described as anaphylaxis. Delayed type hypersensitivity is more commonly observed in dental clinic. It can be related to long term exposure of oral tissues to sensitizing substances manifested as edema, burning and erosive alterations. Assessment of the allergic reaction type can be supported by the distribution and localization of clinical symptoms however definitive determination of allergy is done by an allergy test. Common tests for potential allergens are patch and prick skin test in vivo as well as RAST test in vitro. Prevention of dental allergy occurrences is more preferable, rather than treating them. This is done by detailed and accurate history taking prior to initiation of dental treatment. Treatment of dental allergy is based on removing the sensitizing materials from oral cavity and replace it with alternative dental material. With better understanding of allergic reactions in prosthetic dentistry, prevention, treatment and future avoidance of the conditions are significantly increased and possibility of successful prosthetic restoration is much higher.