Angular cellulitis: meaning, care and warning signs

True cellulitis is a bacterial infection in deeper skin. It commonly presents with an enlarging area that is red or discoloured, warm, swollen and tender. A crack at the corner of the mouth can instead be angular cheilitis, which affects the surface and may be irritated by saliva or complicated by yeast or bacteria.

A clinician looks beyond the label and examines the pattern. A small fissure confined to the mouth angle suggests angular cheilitis, while warmth, diffuse swelling, marked tenderness or redness spreading into the cheek raises concern for cellulitis. Blisters, dental pain, pus, a new product and facial injury can point toward other causes. Cellulitis can follow a break in the skin and may occur with fever or feeling unwell.

Arrange a prompt medical assessment if the area is hot, increasingly painful, swollen or expanding. Do not squeeze, pierce or scrub it, and avoid using leftover antibiotics or steroid cream because the correct treatment depends on the diagnosis. Keep the area gently clean and note whether the border is spreading. If cellulitis is confirmed, prescribed antibiotics should be taken exactly as directed. A clinician may also check for a mouth-corner crack, dental source, athlete's foot elsewhere, diabetes or another entry point for bacteria.

Seek urgent medical help for rapidly spreading redness or swelling, severe or escalating pain, fever with worsening skin changes, red streaks, pus, blistering, dusky skin, confusion, unusual sleepiness, fast breathing, faintness, or difficulty opening the mouth, swallowing or breathing. Facial swelling near an eye also needs urgent assessment. These features matter because infection can extend through tissue or affect the whole body; urgency is based on the warning signs, not on how commonly a diagnosis occurs.

Ask whether the changes fit cellulitis, angular cheilitis, a dental infection or contact irritation; whether an antibiotic or a swab is appropriate; what change should be expected after treatment starts; and which symptoms should trigger emergency care. Mention recent dental problems, skin breaks, recurring foot fungus, diabetes, immune-suppressing medicines and any products already applied.