Subcutaneous emphysema is a rare complication in dentistry, which may lead to diagnostic errors and inadequate therapy. A 17 years old female patient, in whom the separation of tooth roots was performed by the use of air-powered drill during the extraction of the first right lower molar, is presented in this paper. During the intervention, swelling of the right half of the face and the lower eyelid suddenly occurred, accompanied with simultaneous feeling of choking, and pressure in the neck and chest. Because of the suspicion of the allergic reaction, the patient was administered antihistaminic agent, together with parenteral corticosteroid, and was sent to an institution where she was treated as an in-patient. During hospitalization, subcutaneous emphysema of the face and neck was diagnosed by physical and x-ray examination. The emphysema completely disappeared after the use of oxygen and antibiotics.