The correlation between surface microscopy and dermal histology in tetradecane-induced comedones in rabbit ear skin.

Three concentrations of tetradecane and liquid paraffin were applied daily for 4 weeks to the external ear skin of rabbits, and the average diameter of the follicular lesions was measured under the Leitz MZ surface microscope. These observations showed that the increase in the size of follicular lesions with tetradecane was dose-dependent and the maximum diameter was reached on the 14th day. Serial biopsies were also taken for routine histology, and undiluted tetradecane was shown to produce follicular hyperkeratosis, microcomedones, closed comedones and open comedones. A good correlation was obtained between the surface observations and the histological findings. The surface microscope provides a simple and convenient in vivo method for evaluating comedo formation.