DISTRIBUTION AND KERATOLYTIC EFFECT OF SALICYLIC-ACID AND UREA IN HUMAN SKIN

Salicylic acid (SA) and urea are widely used in topical preparations. Using a simple tape stripping technique the effect on the binding forc es within the stratum corneum and the skin absorption of SA and urea w ere studied. The degree of stratum corneum removal was recorded by mea suring the transmission through the tape with a digital light-measurin g instrument. With successive stripping of the skin the amount of tiss ue adhering to the tape decreased. Exposure of the upper arm to 2% SA for 6 h increased the skin material on the tape strips significantly. No significant increase was recorded after 3-hour exposure, or after e xposure to 0.5% SA. Neither did the exposure to 10% urea for 3 or 6 h influence the amount of skin adhering to the tape significantly. Radio chemical analyses showed that the amount of SA and urea in each of the first 6 tape strips was about 5-15 mu g/cm(2). This technique provide s a useful tool to evaluate the binding forces within the stratum corn eum in relation to absorption of topically applied substances.