Abstract
Biopsies taken before and at 30 min., 3, 5 and 7 days after the dry ice press therapy from nevus Ota were examined by light microscopy. Dry ice was pressed for 7 seconds and this procedure was repeated. At 30 minutes after the procedure, no remarkable changes was observed both in the epidermis and in the dermis. At 3 days after the treatment, the dermal melanin-laden cells were round in shape and some were vacuolated. At 5 days after the treatment, the vacuolation and the decrease in number of the dermal melanin-laden cells were more remarkable. At 7 days after the treatment, all dermal melanin-laden cells were round in shape and located at the periphery of the dermal vessels. From these results, the mechanism of the dry ice press therapy seems to be as follows; first there is a degeneration of the dermal melanocytes as a result of the direct effect of freezing, the cell membrane breaks and the melanosomes dispersed in the dermis are partly taken up by monocytes and carried to the regional lymphnode. Some melanosomes travel to the outside in the crust when the tissue damage is relatively severe. The amount of the dermal melanin decreases after dry ice therapy.
