In an open clinical study, efficacy of 5% aqueous solution of lactate for preventing acne was evaluated in 22 patients. Lactate lotion was used topically all over the face twice a day and continued like a cosmetic for 1 year. Systematic antibiotics were given for periods of 4 weeks whenever the disease was severe. The effect of the treatment was evaluated by counting the number of comedones, inflammatory lesions and cysts separately once a month and recording them graphically. The greatest reduction in the lesion counts was achieved in 8-24 weeks for the inflammatory lesions and 8-30 weeks for the comedones. At the end of 1 year 90-100% reduction of the inflammatory lesions was achieved in 40.9% patients and non-inflammatory lesions in 22.7% patients. The remaining patients showed 50-90% reduction, while 2 patients showed less than 50% reduction in the non-inflammatory lesions. Thus, most of the patients showed significant reduction in the lesion counts. Aggravations were associated with the hot and the rainy season and required concomitant treatment with oral antibiotics.