What causes erythema nodosum on the legs?

Erythema nodosum commonly appears as tender, firm lumps over the shins. The skin may look red, purple, or bruised as the lumps settle. Triggers include a recent throat or other infection, some medicines, and inflammatory diseases affecting the bowel or joints. Sometimes no single cause is found. The lumps reflect inflammation rather than a pocket of pus, so squeezing or cutting them can injure the skin and will not treat the underlying process.

Book a medical appointment so the diagnosis and possible trigger can be assessed. Tell the clinician about recent infections, new medicines, joint pain, stomach symptoms, cough, weight change, or other new concerns. Resting the legs, raising them, and using a cool compress may reduce discomfort. Treatment is directed at the trigger and symptoms; prescribed anti-inflammatory medicines or, in selected cases, oral corticosteroid treatment may be considered after infection has been evaluated.

Seek urgent care for severe or rapidly worsening pain, difficulty walking, a very swollen leg, breathing difficulty, chest pain, high fever, or feeling faint. Prompt assessment is also sensible when lumps are associated with a new widespread rash, significant abdominal symptoms, or a medicine reaction.

Ask which triggers fit your history, whether you need tests for infection or inflammation, which medicines may be contributing, and how to manage pain while the lumps settle.