The Effect of Benzoyl Peroxide 9.8% Emollient Foam on Reduction of Propionibacterium acnes on the Back Using a Short Contact Therapy Approach

July 2012 | Volume 11 | Issue 7 | Original Article | 830 | Copyright © July 2012


Benzoyl peroxide (BP) exerts its therapeutic effect for acne vulgaris through reduction of Propionibacterium acnes. A 1.0 to 2.0 log reduction in P acnes has been demonstrated primarily on the face with use of “leave-on” BP formulations, but also with some BP cleansers. In addition to use for facial acne vulgaris, cleanser formulations of BP are commonly used for truncal acne vulgaris due to ease of use on a large body-surface area and to avoid bleaching of fabric. To date, evaluation of P acnes reduction on the trunk has not been well studied with BP formulations, especially with the use of recognized and standardized methods to accurately determine P acnes colony counts. A previous study demonstrated that a BP 8% cleanser did not reduce counts of P acnes on the back when subjects were instructed to apply the cleanser in the shower, allow it to dry for 20 seconds on the skin, and then rinse off the cleanser. Evaluation of specified time intervals between application on the back and rinsing with BP formulations would help to better define the necessary skin contact time associated with high reductions of P acnes (>90%), recognizing also the potential roles of BP concentration and vehicle. This 2 week study using quantitative bacteriologic cultures evaluates the effectiveness of BP 9.8% emollient foam in reducing P acnes levels on the back with 2 minutes of skin contact time and compares results with a BP 5.3% “leave-on” emollient foam formulation. Short contact therapy utilizing a 2 minute skin contact time with BP 9.8% emollient foam used once daily over a 2 week duration was highly effective in reducing the quantity of P acnes organisms on the back and provided comparable colony count reduction to “leave on” therapy using BP 5.3% emollient foam.

J Drugs Dermatol. 2012;11(7):830-833.


Propionibacterium acnes is a common gram-positive microaerophilic organism found on normal skin as part of the commensal flora. Although the quantity of P acnes present on the skin surface does not consistently correlate with the severity of acne vulgaris (AV), a direct association between the proliferation of P acnes and the development of AV lesions is supported by a large body of evidence.1 A very relevant finding is that reductions of adequate magnitude in P acnes organisms correlate directly with clinical improvement after use of many topical and systemic antimicrobial agents used to treat AV, such as benzoyl peroxide (BP) and some antibiotics.1-4 Most available topical antimicrobial preparations used to treat AV exert their therapeutic effect primarily by reducing P acnes as demonstrated by a 1.0 to 2.0 logarithmic reduction in P acnes colony counts, equivalent to a range of 90% to 99% reduction in organisms.3,4
Topical treatment of truncal AV presenting on the chest, back, and shoulders can be very challenging.5-7 Application of topical medication on the trunk (ie, back, chest, and/or upper arms, and shoulders) requires application to a widespread surface with some areas that are difficult to reach on the back. It is important that the appropriate vehicle be selected that can be conveniently and efficiently applied to the entire anatomic field. Formulations such as cleansers and foams are the most applicable for use on the back because they are easy to spread.5-9 Cleanser formulations of BP are commonly used for treatment of AV and are especially applicable for use on the trunk, due to the convenience of application in the shower and minimal potential for bleaching colored fabric. However, there are few published data on P acnes reduction with BP cleanser formulations when used on the face as well as a conspicuous absence of data on P acnes reduction with the use of BP on the back.5-10

“Leave-on” and Non-“Leave-on” Formulations of Benzoyl Peroxide

Benzoyl peroxide is available for topical application to skin using both “leave-on” and non-“leave-on” formulations. A topical “leave-on” therapeutic formulation is one that is applied after gentle cleansing and drying with the intention of being left on the skin for a prolonged period (ie, hours) before any repeated cleansing or attempted removal from the treated area. In the case of BP-containing topical products, there are several studies that have evaluated P acnes reduction and/or therapeutic efficacy in patients treated with “leave-on” gels, creams, foams, or lotions for facial AV.1-4,11 A commonly used type of topical non-“leave on” formulation is a cleanser (or wash), which is applied during the act of washing the skin with a limited duration of cutaneous contact time prior to rinsing. The suggested range of “contact” during skin washing