Increase of mast cells in the alopecia lesion of mice.

A histological investigation was made of the quantitative behavior of mast cells in bald areas on mice and in human alopecia areata. C57BL,W/Wv and +/+ mice with alopecia lesions were examined. In C57BL mice and +/+ mice, the number of dermal mast cells (per square mm) in the bald areas was greater than that in controls. The mean number of mast cells was slightly higher in human alopecia areata than in the controls. Since W/Wv mice lacking mast cells developed alopecia lesions, it seems that mast cells are not necessary for the onset of alopecia areata but could play some part in regrowth.