A multi-sample design for assessing the comedolytic activity of topical products

Facial comedolytic studies allow testing of a maximum of two products. The upper back provides a larger area with a more uniform distribution of microcomedones for comedolytic studies.

To design a multi-sample method for assessing comedolytic activity of topical products on the back. The effect of season on product discrimination was also explored.

Three cleansing formulations (products B, C and D), a negative water control and 0.025% Retin-A cream (positive control) were tested. Seven subjects were recruited in summer and nine in fall. Products were applied for 8 weeks, comedolysis was assessed by visually evaluating cyanoacrylate follicular biopsies taken at baseline and post-treatment.

In all data sets (summer, fall and combined), sites treated with Retin-A had a significantly lower number of microcomedones as compared to the negative water control. In addition, cleansers B and D showed a significant reduction from baseline in the fall and combined (summer and fall) data, but not in summer data alone indicating different responses to treatment during the year.

The design was sensitive enough to detect differences between cleansing formulations under normal washing conditions. Reduced sensitivity observed during summer suggests hot humid conditions may decrease the comedolytic performance of topical products.