Swollen corner of the lip: causes and care

Saliva collecting in the crease, lip licking, dry weather, or a dental appliance can irritate the corner and cause cracking. A sore that is red, tender, and crusted may have become infected. Burning or blisters can occur with a cold sore. Sudden swelling after a new product, food, medicine, or dental exposure may be allergic. Angioedema can cause deeper lip swelling and may involve more than the corner.

Check whether the skin is split, moist, blistered, scabbed, or leaking fluid. Recurrent cracking, especially with mouth discomfort, deserves a clinician’s examination rather than repeated self-treatment.

Wash with water, pat dry, and apply a plain protective ointment to the outer skin if it does not sting. Avoid licking, picking, fragranced balms, and spicy or acidic foods that burn the split. Do not share lip products or towels if blisters or drainage are present. A clinician can decide whether an antifungal, antibiotic, antiviral, or anti-inflammatory treatment is appropriate; avoid choosing one based on appearance alone.

Seek emergency help for breathing difficulty, throat or tongue swelling, faintness, wheezing, or trouble swallowing. Arrange prompt care for rapidly spreading redness, warmth, pus, fever, severe pain, facial swelling, or difficulty opening the mouth. Make an appointment when the corner repeatedly splits, does not improve, or affects eating and drinking.

Ask what the crack or swelling resembles, whether saliva or a product may be irritating it, whether a swab or other test is useful, and which changes should prompt same-day care.