The study was performed to examine the relationship between defense reaction of skin to local stimulation and enzymological change of the exudates produced by the application of Unguentum vesicans. The activities of glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), lactic dehydrogenase (LDH) and LDH isozyme were measured about exudates and sera in hepatitis, cancer, lung tuberculosis, nephritis and other conditions. The results of the study are summarized as follows. (1) The activities of GOT, GPT and LDH of exudates were higher than the activities of sera in almost cases. The GOT activity of exudate was paralleled to elevation of GOT activity of serum in hepatitis and cancer, and similar correlation of GPT activity was observed in hepatitis. There was not correlation of changes of LDH activity between exudate and serum. (2) There was not the relationship between the strength of local inflammatory responses and the enzyme activities of exudates. (3) LDH isozyme of the exudate was similar to isozyme pattern of epidermis. (4) The most of GOT and GPT of exudate were released from blood, but LDH of the exudate originated in epidermis.