Glycolic acid causes disaggregation of corneocytes at the lower, newly forming levels of stratum corneum. This property may permit efficient clinical controls of different conditions, i.e. dry skin, ichthyosis, follicular hyperkeratosis, and others characterized by retention of stratum corneum. Our study shows a strong increase (compared to the previously not treated area) in Langerhans cells levels (CD1a+) in the chronically photoexposed epidermis of 3 subjects (aged 71, 68 and 59) treated with topical glycolic acid, applied in concentration of 70% in office procedures, with concomitant daily home application of 10% concentration. The molecular mechanism of action of glycolic acid on human skin remains to be clarified, but since Langerhans cells are closely related to cutaneous cell-mediated immunity, it has been suggested that their well-documented reduction in elderly skin, especially in skin habitually exposed to ultraviolet rays, may be related to immunosurveillance of the skin and particularly to photocarcinogenesis. On the basis of our preliminary data, we hypothesize that glycolic acid exerts some beneficial effects on photoaging-reduced immunosurveillance by increasing the levels of CD1a+ cells in human skin.