Nitric oxide (NO) is produced by a wide variety of human cells and affects physiological and pathophysiological processes. In this study, we demonstrated for the first time that neuronal NO synthase (NOS) is expressed in eosinophils infiltrating into the dermis and follicular epidermis in eosinophilic pustular folliculitis (EPF). EPF is a cutaneous inflammatory follicular disorder first described in Japan. The clinical and histological features of EPF are characterized by erythematous papules, infiltration of numerous eosinophils, and a spongiotic appearance of the follicular epidermis, but the pathophysiology of EPF remains unclear. Our results suggest that NO produced from eosinophils plays an important part in the pathogenesis of EPF. Furthermore, we speculate that NOS inhibitors may be useful in the management of EPF.