Erythema nodosum is the name given to extremely tender lumps on the legs and sometimes the arms. They are caused by inflammation of the fat beneath the skin. The bumps look like bruises. They change color in the same way, from pink to blue to brown. They are often accompanied by fever, joint pain, and redness around the eyes. They may continue to erupt for a week to 10 days. They will eventually resolve. It often resolves within 1-2 months.