Erythema nodosum is an inflammatory reaction deep in the skin characterized by the presence of tender red lumps or nodules ranging in size from 1 to 5 centimeters most commonly located over the shins but occasionally involving the arms or other areas. The causes of erythema nodosum include medications (sulfa-related drugs, birth control pills, estrogens, iodides and bromides), strep throat, cat scratch disease, fungal diseases, infectious mononucleosis, sarcoidosis, Behcet’s disease, inflammatory bowel disease (Crohn’s disease and ulcerative colitis), and normal pregnancy. In many cases, no cause can be determined. Erythema nodosum may be self-limited and go away on its own in 3 to 6 weeks. If treatment is needed, the underlying condition is treated and simultaneously treatment is directed toward the erythema nodosum. This can include antiinflammatory drugs and cortisone by mouth or injection. Colchicine is sometime used effectively to reduce inflammation.