Stimulatory effect of histamine on normal human melanocytes in vitro.

Normal human epidermal melanocytes became swollen and more dendritic and the immunoreactive tyrosinase increased markedly when they were cultured for 2 days with 5 microM of histamine. These results suggest that high dermal concentrations of histamine may be responsible for the induction of skin pigmentary changes associated with local proliferation of mast cells such as in urticaria pigmentosa and systemic mastocytosis.