Abstract
In three cases of negative patch test, electron microscopic investigation was performed on the erythematous lesions in scratch patch test. In epidermis, intercellular edema and infiltration of lymphocytes and macrophages were observed. Langerhans cells showed the features of accelerated activity, having enlarged endoplasmic reticlum, large mitochondria, lots of Birbeck's granules and centriole. Furthermore, lymphocytes apposed to Langerhans cells and macrophages in the intercellular spaces of the epidermis. From the results above, it is recognized that scratch test is applicable in clinical practice.
