What should you know about infection in a swollen lip?

A small break in the lip can let germs enter, sometimes after biting, shaving, a cold sore, piercing, or dental infection. Infection may produce a painful lump, yellow crust, drainage, bad taste, fever, or redness that extends beyond the original area. Swelling that appears suddenly after food, medicine, or an insect sting may instead reflect allergy or angioedema. The timing, skin appearance, mouth symptoms, and dental history help a clinician distinguish these possibilities.

Gently rinse the mouth if it is involved, keep the outer lip clean, and use a cool compress wrapped in cloth for comfort. Avoid popping blisters or abscesses and avoid products that sting. Wash hands often and do not share cups, towels, razors, or lip balm. A clinician may need to treat a bacterial, viral, fungal, or dental source, so avoid self-starting leftover medication.

Get emergency help if swelling affects the tongue or throat, breathing or swallowing becomes difficult, or you feel faint. Seek prompt assessment for fever, pus, severe pain, rapidly spreading redness, facial swelling, or trouble opening the mouth. A persistent or recurrent swelling also deserves review, even when discomfort is mild.

Ask whether the source is the skin, mouth, or teeth; whether testing is needed; what treatment to use; and which changes should prompt re-evaluation.