A patient seen yesterday returns the next day with a swollen lip. What is the likely diagnosis?

Correct answer: C. Angioedema

• A. Cellulitis would be firm, hot, erythematous and tender, with systemic signs and an identifiable odontogenic source.
• B. An injection haematoma would be bruised and discoloured, and appears immediately rather than the following day.
• C. Correct. Diffuse, non-pitting, non-erythematous swelling of the lip appearing within hours to a day points to angioedema — commonly a reaction to latex, an anaesthetic component, or a drug such as an ACE inhibitor.
• D. A mucocele is a discrete bluish translucent nodule, not diffuse lip swelling.

Note: The danger is airway involvement. Any swelling of the tongue, floor of mouth or larynx is a medical emergency.