Efficacy of Benzoyl Peroxide (5.3%) Emollient Foam and Benzoyl Peroxide (8%) Wash in Reducing Propionibacterium acnes on the Back

June 2010 | Volume 9 | Issue 6 | Original Article | 622 | Copyright © June 2010

James J. Leyden MD

Department of Dermatology, University of Pennsylvania, Philadelphia, PA

Background: Topical treatment of acne vulgaris on the back is challenging largely due to the extensive broad surface with difficult to reach areas. A “leave-on” foam is suited for application to the trunk due to ease of application and spreadability. Prior to this trial, no data on Propionibacterium acnes (P. acnes) reduction on the back has existed for any benzoyl peroxide (BP) formulations or other acne treatments.
Objectives: To evaluate the effectiveness of BP (5.3%) emollient foam and BP (8%) wash in reducing P. acnes levels on the back.
Methods: Five-week open-label single-center study of 20 healthy subjects (>18 years old), colonized with P. acnes on their backs (>10,000 colonies per cm2). Subjects were treated once daily with BP (5.3%) foam for two weeks; no treatment in week 3, and BP (8%) wash once daily for two further weeks. Quantitative bacteriologic cultures obtained at baseline and weeks 1, 2, 3, 5 and 6. Results: Nineteen evaluable patients. Total P. acnes counts were reduced by 1.9 log (one week) and 2.1 log (two weeks) with BP (5.3%) emollient foam. BP (8%) wash did not reduce P. acnes counts after two weeks.
Discussion: BP (5.3%) emollient foam was superior to BP (8%) wash in reducing P. acnes on the back. The lack of effect of BP (8%) wash is surprising in view of the demonstrated results on the face and warrants further study.


The effectiveness of topical acne therapy is related to adherence with the regimen by the patient, which is influenced directly by the ability to apply anti-acne preparations appropriately. Although truncal acne is less well studied than facial acne, there has been increasing attention on its evaluation and management.1,2
Most patients with truncal acne present with concurrent facial acne: a study of truncal acne demonstrated that 48 percent of patients had acne solely on the face while 52 percent also had truncal acne.1 Only two percent of patients had solely truncal acne. In a more recent study of patients referred by primary care physicians to dermatologists for the treatment of acne, the prevalence of facial acne was 93 percent while the prevalence of chest and back acne was 45 and 61 percent, respectively.3
Topical treatment of truncal acne presenting on the chest, back and shoulders can be challenging as it requires application of anti-acne preparations to a difficult to reach, broad surface area. In addition, there is no effective treatment for truncal acne scarring once it develops, so effective acne therapy is important to prevent lesion development and scar formation.4
Due to the extensive surface area of the back, it is important that the appropriate vehicle be selected that can be conveniently and efficiently applied. Formulations that exhibit ease of spreadability and lack of residue, such as cleansers and foams, may be more applicable for truncal application.5,6
Benzoyl peroxide (BP) is extensively utilized as a topical agent for the treatment of acne.7 BP alone or in combination with clindamycin reduces Propionibacterium acnes (P. acnes) and reduces the emergence or proliferation of antibiotic-resistant P. acnes strains.7–9 Importantly, P. acnes organisms resistant to BP have not been identified nor would it be expected since this agent is a non-antibiotic antimicrobial.7
BP exerts its therapeutic effect in acne through reduction of P. acnes as demonstrated by a 1.0–2.0 logarithmic colony reduction on the face. “Leave-on” BP formulations have been shown to provide greater reduction in P. acnes than “wash-off” formulations.10,11 BP “wash-off” formulations have been shown to be effective in reducing P. acnes populations on the face.12,13 Interestingly, the author could find no published data on P. acnes reduction on the back for any BP formulation.
“Wash-off” formulations of BP are frequently recommended for the treatment of truncal acne due to patient convenience of application in the shower as well as to minimize bleaching potential.14,15
The purpose of this study was to evaluate the in vivo effects on P. acnes levels on the back with use of a BP (5.3%) emollient foam and a BP (8%) wash by quantitative microbiologi-