An allergic reaction can make the lips swell. The reaction may be caused by sensitivity to certain foods or beverages, drugs, lipstick, or airborne irritants. But frequently, the cause of the swelling remains a mystery.
A condition called hereditary angioedema may cause recurring bouts of swelling. Nonhereditary conditions—such as erythema multiforme, sunburn, cold and dry weather, or trauma—may also cause the lips to swell. Lip swelling on its own is not dangerous. However, when lip swelling is caused by angioedema, an accompanying swelling in the mouth, throat, and/or lower airways can be fatal.
Treatment depends on the cause. When a cause can be identified and then eliminated, the lips usually return to normal. A corticosteroid ointment is sometimes used to reduce swelling caused by an allergic reaction. Occasionally, excess lip tissue may be removed surgically to improve appearance.