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Exfoliating acids

Mandelic acid

Also listed as AHA

A larger, slower-penetrating AHA often chosen for sensitive or darker skin. Used in acne peels and now in deodorants that lower skin pH.

Limited evidenceTypical strength: 5-10% leave-on

What it is

Mandelic acid is an AHA with a bulky ring structure, so it penetrates more slowly than glycolic acid and tends to sting less. It also has some antibacterial activity. Clinics use it in peels, often combined with salicylic acid, for acne and pigmentation, especially in darker skin where irritation-driven darkening is a concern.

In body care it appears mainly in 'whole-body' deodorants and washes, where the acid is meant to lower skin pH and slow the bacteria that cause odour rather than to exfoliate.

How strong is the evidence?

Limited evidence

Evidence comes mostly from small peel studies. In a 44-patient comparison, a 20% salicylic–10% mandelic acid peel beat a 35% glycolic peel for active acne and post-acne dark marks with fewer side effects; a Cochrane review, looking at participant-rated improvement, found little difference and rated the evidence low quality. Leave-on mandelic products and mandelic deodorants have little published testing.

What it's used for, checked

Acne (as a peel)

Mixed

Salicylic-mandelic peels helped acne in a small comparative trial; the combination makes it hard to credit mandelic acid alone.

Post-acne marks and uneven tone

Mixed

Improved in the same small peel trial.

Gentler exfoliation for sensitive skin

Mixed

Its slower penetration makes it milder in practice, but head-to-head tolerability trials are few.

Odour control in deodorants

Unproven

Lowering skin pH plausibly slows odour bacteria, but independent trials of mandelic acid deodorants are lacking.

Who should be careful

  • Like other AHAs it can increase sun sensitivity; use sunscreen on exposed skin.
  • Underarm use can sting right after shaving; apply to unbroken skin.

The studies

Every citation is checked against its PubMed record.

  1. Glycolic acid peels versus salicylic-mandelic acid peels in active acne vulgaris and post-acne scarring and hyperpigmentation: a comparative study.
    Garg VK, Sinha S, Sarkar R · Dermatologic Surgery · 2009 · Comparative trial

    44 patients in India with acne and post-acne marks had six fortnightly peels of 35% glycolic acid or 20% salicylic–10% mandelic acid; both helped, and the salicylic-mandelic peel worked better on active acne and pigmentation with fewer side effects.

  2. Topical azelaic acid, salicylic acid, nicotinamide, sulphur, zinc and fruit acid (alpha-hydroxy acid) for acne.
    Liu H, Yu H, Xia J, Liu L, Liu GJ, Sang H, Peinemann F · Cochrane Database of Systematic Reviews · 2020 · Systematic review

    49 trials (3,880 people): azelaic acid is probably less effective than benzoyl peroxide and about as effective as tretinoin for acne; evidence for salicylic acid, nicotinamide and alpha-hydroxy acids was low or very low quality, from small head-to-head trials, and no conclusions were reported for zinc or sulphur.