A 45% mandelic acid peel — an alpha hydroxy acid derived from hydrolysis of bitter almond extract — is as effective as a 30% salicylic acid peel for reducing the severity of mild to moderate facial acne vulgaris, study data in the Journal of Cosmetic Dermatology suggest. Despite their similar efficacy profiles, the 45% mandelic acid peel is associated with better safety and tolerability outcomes than the 30% salicylic acid peel.

Patients with mild to moderate facial acne (grade 1 and grade 2) were randomly assigned to receive either a 30% salicylic acid peel (n=25) or a 45% mandelic acid peel (n=25) once every 2 weeks for a total of 12 weeks. After and between each session, patients were instructed to apply a broad-spectrum SPF 30 sunscreen and were asked to not exfoliate their skin or use facial masks on the treatment area(s). At baseline and at each study visit, acne severity was assessed using the Michaelsson acne scores (MAS).

Severity was based on the individual count of comedones, papules, and pustules. In addition, a blinded dermatologist assessed the improvement in acne at the end of the 12-week study period. A >50% reduction in MAS was graded as “good improvement,” a 21% to 50% reduction in MAS was graded as “fair improvement,” a 11% to 20% reduction in MAS was graded as “poor improvement,” and a 0% to 10% reduction in MAS was graded as “no change.”

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At 12 weeks, patients who received the 30% salicylic acid peel had a significantly greater overall percentage reduction in mean comedone counts vs those who received the 45% mandelic acid peel (73.4% vs 59.66%, respectively; P =.044). Both groups had a significant decrease in mean papule counts from baseline to 12 weeks (P <.001 for both), with the 45% mandelic acid peel demonstrating an earlier decrease at 4 weeks vs 6 weeks in the salicylic acid group. From 4 weeks to the end of the study, a 45% mandelic acid peel was associated with a greater overall percentage decrease in mean papule counts than the 30% salicylic acid peel (85.98% vs 76.9%, respectively; P =.004).

No difference was found between salicylic acid and mandelic acid groups with regard to the overall percentage reduction in mean pustule counts at 12 weeks (95.33% vs 95.69%, respectively; P =.86). There was also no difference between the salicylic acid and mandelic acid peels in terms of the overall percentage reduction in mean MAS at 12 weeks (78.56% vs 76.31%, respectively; P =.12). All patients had a good improvement (ie, >50% reduction in MAS) in acne at the end of treatment. More patients in the salicylic acid group experienced postpeel erythema than patients in the mandelic acid group (9 vs 2, respectively).

Limitations of the study include the small sample size as well as the lack of follow-up to identify rate of recurrence.

The investigators suggest that the superior safety profile of the 45% mandelic acid peel is “attributed to the large structure of mandelic acid, leading to its slow and uniform penetration in the epidermis, making it an ideal peeling agent for the sensitive skin of the patients with severe acne and hyperpigmentation.”

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Reference

Dayal S, Kalra KD, Sahu P. Comparative study of efficacy and safety of 45% mandelic acid versus 30% salicylic acid peels in mild-to-moderate acne vulgaris [published online September 25, 2019]. J Cosmet Dermatol. doi:10.1111/jocd.13168