Immediate contact reactions to benzoic acid and the sodium salt of pyrrolidone carboxylic acid Comparison of various skin sites

Benzocc acid (BA) and the sodium salt of pyrrolidone carboxylic acid (NaPCA) were tested in 13 healthy persons to obtain information about, firstly, the irritant properties of NaPCA and, secondly. the reactivity of various skin sites. BA at 16, 8, and 4 mM pet., anil NaPCA at 50, 25, 12.5, and 6.25% in water, were applied to the forehead, check, neck and upper back Erythema reatt.imis were observed visually, and the changes in ihe skin blood How were monitored using a laser‐Floppier flowmeter. BA at 16 mM mcreused Wood flow on the cheek of 12 tesl subjects, and on the neck, forehead and upper back of 6 subjects, but S and 4 mM BA elicited reactions only on the cheek. NaPCA caused reactions on the upper back of 3 test subjects only, but not on oilier test sites.