R SKIN CARE 95
Do squalene peroxides cause acne?
Norman Miller, Irina Miller - Kutanios
Affecting an estimated 230 million people, acne vulgaris is the commonest chronic skin condition seen by physicians, and appears to have increased by almost 50% between 1990 and 2019.1
The reason for the rise is not clear. Although much has been written about the
possible effects of changes in diet, particularly fat and chocolate, a recent systematic review concluded that more information is needed before any conclusions about these or any other nutrients can be made. Other plausible explanations for the rise in prevalence under consideration are obesity,2 pollution.2,4
and atmospheric The primary lesion is of the pilosebaceous
units, involving sebum accumulation, hyperkeratinisation, inflammation, infection, and infiltration with neutrophils and macrophages.5
Inflamed lesions can leave
lifelong scars, and the condition can be a cause of loss of self-esteem leading to chronic anxiety and depression.6
The case for Cutibacterium acnes Infection of the lesions with Cutibacterium acnes is so common that it has long been suspected as the primary cause. As a result, antibiotics have become a mainstay of treatment. In the USA, dermatologists prescribe more oral antibiotics than physicians of any other speciality, mostly for acne, even though the reductions of inflamed lesions have averaged little more than 10% compared with placebo in randomised controlled trials.7 In an attempt to counter the rise in antibiotic resistance that has been an inevitable consequence,8 reported,9
of Dermatology,7
rates of up to 60% having been guidelines of the American Academy and others,10
recommend that
antibiotics should be used only in combination with other agents, such as retinoids and benzoyl peroxide. The issue would be less significant if it were limited to acne. But this is not the case. C. acnes is a cause of other infections, especially after surgery and implants.11 Long-term use of antibiotics can also lead to resistance in other pathogenic bacteria, and
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disturb the microbiomes of both the skin and alimentary tract.12
Accordingly, it is important
to know whether C. acnes infection really is the causal agent, and not secondary to a fundamental disorder of pilosebaceous units. The case for C. acnes being only an opportunistic infection in acne is significant. The bacterium is a normal skin commensal in the majority of people, especially in areas
containing sebaceous glands.13 As it is a
lipophilic and facultative anaerobe, it would be surprising if it were not commonly present in pilosebaceous units. When Puhvel et al grew cultures from 138 they found that 68% were
healthy units,14
colonised with C. acnes. Bojar and Holland found that the density of C. acnes in healthy units varied by more than one million-fold, with no evidence of inflammation in even the most densely populated.13
Other studies in which
cultures were grown from inflamed units have found that C. acnes was not invariably present. In one such investigation, Leeming et
al found infection rates of 68, 19, and 52%, respectively, for C. acnes, Staphylococci, and the commensal yeast Melassezia, a profile very similar to that previously reported by the same authors for non-inflamed lesions.15 Clinical trial results also seem at variance
Figure 1: Inflamed acne vulgaris in a young woman
with C. acnes being the culprit. In data from eight randomised controlled trials, treatment with topical antibiotics reduced the number of inflamed lesions by an average of 11%, whereas
August 2025 PERSONAL CARE
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