Dermatologica. 1987;175 Suppl 2:29-35.

Immunohistochemical characterization of the cellular infiltrate in severe alopecia areata before and after minoxidil treatment.

Fiedler VC,

The mechanism of minoxidil-induced hair regrowth in the treatmen of alopecia areata hair loss (AA) is unknown. In vitro studies suggest that pharmacologic tissue levels of minoxidil may have both epithelial and T cell effects.snip...Nonresponders (that is peoe with no hair regrowth) showed none of these changes. Biopsies from 34 patients subsequently treated with oral minoxidil 5 mg q. 12 h showed no further changes in perifollicular total T, helper-inducer T or suppressor-cytotoxic T cell counts; they did, however, demonstrate significant decreases in perifollicular Langerhans cell and activated T cell counts, and nearly significant decreases in perifollicular monocyte counts. It is possible that minoxidil may be altering a presumed follicular chemoattractive stimulus to a variety of cell types. Decreases in activated T cell counts suggest the possibility of direct immunomodulatory effects of minoxidil on T cells which might contribute to a hair regrowth response in AA.