Measurement of skin-fold thickness in the guinea pig. Assessment of edema-inducing capacity of cutting fluids, acids, alkalis, formalin and dimethyl sulfoxide.

The rabbit has been used for decades for predictive testing of skin irritancy, but in recent years, the guinea pig has been suggested as an alternative, especially for assessment of one of the components of the irritant reaction: edema (fluid accumulation). A method based on skin-fold measurements with Harpenden calipers has been developed and modified. In previous papers, experience with sodium lauryl sulphate, nonanoic acid and industrial solvents was reported. The present results concern the use of cutting fluids, buffered and unbuffered acid and alkaline solutions, formalin and dimethyl sulfoxide. This inexpensive and comparatively unsophisticated method afforded clear dose-response relationships and good discriminating power. The only exception was the acid and alkaline solutions, where no changes in skin-fold thickness were observed despite their documented irritant potential. The appearance of erythema (visual scoring) and the increase in skin-fold thickness, and their relationship, are discussed with some illustrative examples. The method described is now well standardized and is suited for predictive testing of the edema-inducing capacity of chemicals and products.