What Causes Sudden Swelling of the Upper Lip?

Sudden swelling of the upper lip may be caused by an allergic reaction to a contact allergen or by an insect bite. It is advisable to visit the dermatology department of a reputable hospital for evaluation. If the swelling is allergy-related, consult your physician about taking antihistamine medications and applying topical corticosteroid ointments as adjunctive treatment. Promptly identify the specific allergen and avoid future exposure.