Our expert says:
Chronic Erythema nodusum is rare - most lesions should clear up within 6 weeks. It is an inflammatory disease of the subcutaneous ( under the skin) tissue and is usually an allergic ( hypersensitivity) reaction to certain bacteria, viruses, fungi or chemicals - usually sulphonamides ( found in certain antibiotics, diuretics, or sulpher containing foods) , the contraceptive pill, sulphonyl urea ( diabetes medication). The treatment of ibuprofen or aspirin or cortisone is given to clear up the inflammation that has already happened. I think in your case the cause must be found and maybe you should see a rheumatologist to try avoid whatever is triggering this.
this is a bit academic but may be interesting to you: http://www.emedicine.com/derm/topic138.htm
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