The expression of semaphorin 3A was investigated in normal and atopic skin from atopic dermatitis (AD) patients. In addition, the effects of psoralen and ultraviolet A (PUVA) on semaphorin 3A levels in AD and the relationship between epidermal innervation and semaphorin 3A levels were investigated. Semaphorin 3A is expressed in normal human epidermal keratinocytes and its expression was much decreased in the epidermis of AD patients. The intraepidermal nerve fibers seen in AD were significantly decreased after PUVA. An increase in the expression of semaphorin 3A in the epidermis decreased the densities of nerve fibers there (Takamori, K. et al. 10th Int Congr Dermatol (May 20-24, Prague) 2009, 100).