Eugenol is an active, principal aromatic liquid responsible for several pharmacological activities. It is widely used in dental practice to relieve pain arising from various sources, such as pulpitis and dentinal hypersensitivity. As a primary irritant and sensitiser, it is known to cause contact urticaria as well as chronic urticaria. However, eugenol causes allergic contact dermatitis, possibly because it can react directly with proteins to form conjugate and reactive haptens. It is found that eugenol in various dental preparations-especially in the case of some zinc oxide–contains preparations such as periodontal dressings and root canal cements. This can cause hypersensitivity when it comes in contact with gingiva or teeth. This article presents a case of immediate allergic contact urticaria to eugenol during dental treatment.