Abstract: Methods and a compositions are provided for treating a skin proliferation disease such as psoriasis to inhibit the proliferation of epidermal cells, particularly keratinocytes and to reduce the symptoms of erythematous scales associated with the disease. The method comprises administering to a mammalian host with a skin proliferation disease a composition comprising an effective amount of an aminoguanidine composition, generally in a pharmaceutically acceptable carrier. The invention also provides a composition comprising an aminoguanidine composition which can be formulated in a pharmaceutically acceptable carrier, in a topical application form or for oral administration. The composition finds use in alleviating symptoms associated with the disease, such as reducing size, thickness or scales of a psoriatic lesion, reducing erthema, decreasing itching and decreasing induration.