Why do products labeled as noncomedogenic still cause acne?

Zoe Diana Draelos, MDNoncomedogenic has become a popular claim listed on products designed for acne sufferers.  Many dermatologists may have wondered, however, why patients who use noncomedogenic products still develop acne.  For this reason, it is worthwhile examining how this claim is substantiated.  Comedogenicity testing is performed on the backs of persons who demonstrate comedone formation with cyanoacrylate biopsy.  The number of comedonal plugs removed in a given area is counted under a low power microscope. 

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Once the ability to form comedones is established, the product for testing is placed on the back under an occlusive patch that is changed frequently for 21 days.  At the end of the test period, the cyanoacrylate biopsy is repeated and the number of comedones removal again counted.  If there is no increase in the comedone count, the product is termed noncomedogenic.

Notice that this testing method only examines the effect of the product on open comedone formation.  It does not assess closed comedones, papules, or pustules.  Thus, it is quite possible to develop other acne lesions besides blackheads with the product, since it was not tested for its ability to promote any other type of acne lesion.

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