Alopecia is a Latin word meaning hair loss or baldness and includes many types of hair loss. The underlying cause of AA is unknown, but recent evidence suggests that it is a chronic inflammatory disease of the hair follicles. Based on the histological evidence of peripheral follicular fibrosis and an increase in the number of mast cells - which can increase the synthesis of elastic fibers - it appears that there may be a link between mast cells and alopecia. The present cross-sectional descriptive-analytical study was performed on formalin and paraffin-embedded tissues of patients diagnosed with alopecia, as well as 20 paraffin-embedded scalp samples of "healthy" patients without reporting Alopecia. In order to evaluate the number of mast cells, Giemsa cytochemical staining was performed. The results show that the mean number of mast cells in AA and AS patients was 18 and 19, respectively, which did not show a significant difference. However, this rate was 18.75 in patients with Alopecia and 6.5 in the control group, which shows a statistically significant difference between the two. Also, the number of mast cells in the biopsy of patients with alopecia was significantly higher than normal individuals, which indicates the role of these cells in the pathogenesis of alopecia.