Half of my bottom lip is swollen: what should I know?

Swelling limited to one side can follow a bite, a cracked lip, a new cosmetic product, dental work, or pressure from biting the lip. A tender area with warmth, spreading redness, pus, fever, or worsening pain can point to infection. Sudden swelling after food, medicine, or a sting can be part of angioedema, which may occur with hives or itching. A local lump, blister, or sore may give the clinician another clue.

Stop any newly used lip product and rinse the area gently with cool water. A cool compress held against the lip for short periods may ease discomfort. Do not squeeze a blister or suspected bite, and avoid licking or repeatedly touching the swelling. Note when it began, what you ate or applied, recent dental treatment, and whether it is changing. Arrange a medical assessment if it does not settle, keeps returning, or is accompanied by pain, warmth, a sore, or fever.

Seek emergency help immediately if swelling involves the tongue or throat, breathing or swallowing becomes difficult, your voice changes, you feel faint, or widespread hives appear. These can signal a serious allergic reaction. Prompt same-day care is also sensible for rapidly increasing swelling, severe pain, fever, or redness spreading beyond the lip.

Could this be an allergy, infection, bite, or dental-related irritation? What changes would require urgent review? Should I avoid a particular product, food, or medicine while the cause is being assessed?