Follicular Biopsy Study

Evaluation of the Comedogenic Potential of a Test Material in Human Subjects Using the Follicular Biopsy Method

This study is an alternative method for determining the comedogenic potential of a test material and is performed on subjects’ upper backs rather than under normal facial use conditions, as described in the Acnegenicity/Comedogenicity summary. Eurofins CRL runs panels of 15 or 18 subjects in order to complete the study with 12 or 15 subjects. Test products may be placed on a shared panel with other Sponsors’ products. If more than 15 subjects are required, your test product will be tested on 2 or more panels or you may request an exclusive panel.


In this study, test products are applied to occlusive patches that are then adhered to the upper backs of subjects every Monday, Wednesday and Friday for 4 weeks.Follicular For potentially irritating products and with Sponsor approval, semi-occlusive patches may be used in place of occlusive patches. Patches are removed, sites are graded for irritation, and fresh product/patches are reapplied at each visit, allowing for continued skin exposure over the 4 week period. A blank (undosed) patch serves as a negative control and a patch dosed with acetylated lanolin alcohol serves as a positive control. At the end of the 4 week period, a follicular biopsy is taken at each site by placing a drop of cyanoacrylate glue on a microscope slide and holding it against the skin on the exposed site for 1 minute. The slide is gently removed from the skin, extracting any microcomedones. Within 1 week of study completion, the slides are evaluated under a microscope and extracted microcomedones, which appear as cylindrical horny impactions surrounding vellus hairs, as well as all follicles in the sampled area are enumerated.

Interpretation & Reporting of Results

The ratio of microcomedones to follicles in the sampled area will be determined for each subject for each test site. Appropriate statistical analysis will be applied, comparing the microcomedone/follicle ratio of each test product to that of the negative control site. Test products for which the ratio is not significantly greater than that of the negative control will be considered non-comedogenic. The negative control site is compared to the positive control site in order to validate the study.

Study results will be available after statistical analyses have been completed. A Final Report will follow, listing irritation scores, microcomedone/follicle ratios and applied statistical analysis.

Scheduling a Follicular Biopsy Study

Generally, Eurofins CRL runs one to two shared panels per month. To reserve a spot for your test sample(s) or to request an exclusive panel, please contact your Client Services representative at 732-981-1616 or contact us by e-mail: