Two discrete psoriatic lesions with a similar size (approximately coin-sized) and clinical severity are selected in each patient. Clinical assessment of psoriatic lesion severity is performed at the baseline and at 1 and 2 (end of treatment) using the scores of erythema, induration, scaling on a scale of 0-4 by two observers. Since STA-21 inhibits Stat3 activation, which is essential for disease activity of psoriasis, topical application of 0.2% STA-21 in Vaseline should improve psoriasis in two weeks.