Glycolic Acid vs Mandelic Acid: Which AHA Is Right for You?

Glycolic acid and mandelic acid sit at opposite ends of the AHA potency spectrum. Glycolic acid (76 Da) is the smallest and most penetrating alpha hydroxy acid; mandelic acid (152 Da) is roughly twice as large, penetrates more slowly, and carries a structural feature no other common AHA shares - partial lipophilicity. That phenyl group makes mandelic acid uniquely suited for acne-prone skin, darker skin tones, and anyone who needs gentler chemical exfoliation without sacrificing pore-level activity. Understanding the trade-offs between these two acids is the key to choosing the right one.

The Science: Molecular Weight and Lipophilicity

All AHAs exfoliate by disrupting corneodesmosomes - the protein structures that hold dead cells together in the stratum corneum [1]. Smaller molecules penetrate more easily and deeply. This is why glycolic acid, at 76.05 Da, is the most potent AHA: it reaches deeper layers of the stratum corneum faster than any other member of the family [2].

Mandelic acid has a molecular weight of 152.15 Da - almost exactly double that of glycolic acid. By the molecular weight rule alone, mandelic acid should be a weak exfoliant with limited clinical utility. But mandelic acid has a structural property that changes the equation: a phenyl (aromatic) ring attached to its carbon backbone.

Why Lipophilicity Matters

Most AHAs are water-soluble. They work well on the water-rich surface of the stratum corneum but cannot penetrate through the oily sebum that fills pores. This is why dermatologists traditionally recommend salicylic acid (a BHA) rather than AHAs for acne - salicylic acid is lipophilic and can dissolve into sebum.

Mandelic acid's phenyl group gives it partial oil solubility, placing it somewhere between purely water-soluble AHAs (like glycolic and lactic acid) and fully lipophilic BHAs (like salicylic acid) [3]. This means mandelic acid has a degree of pore-penetrating ability that glycolic acid and other standard AHAs lack. It does not match salicylic acid's full lipophilicity, but it offers a middle ground that makes it a credible option for acne treatment in people who cannot tolerate salicylic acid or who prefer an AHA-based approach.

Penetration Speed and Depth

The combination of higher molecular weight and partial lipophilicity gives mandelic acid a distinct penetration profile. It enters the stratum corneum more slowly than glycolic acid, producing a more gradual exfoliating effect with less acute irritation [4]. Where glycolic acid rapidly dissolves desmosomes in the outermost cell layers [5], mandelic acid works at a slower pace - which is a disadvantage for aggressive resurfacing but an advantage for people whose skin reacts poorly to fast, deep-penetrating acids.

Glycolic Acid: Profile and Strengths

Glycolic acid is the workhorse of the AHA family. Derived from sugarcane, its small molecular size allows it to penetrate the stratum corneum more uniformly and deeply than any other AHA, which translates to measurable advantages for several skin concerns.

Surface Texture and Smoothing

Glycolic acid excels at smoothing rough, uneven skin texture. By efficiently removing the outermost layers of dead cells, it creates a more uniform skin surface. A 2025 network meta-analysis of 23 RCTs and 3,905 participants confirmed glycolic acid's efficacy for reducing skin roughness [6]. No other commonly available AHA matches glycolic acid's resurfacing ability at over-the-counter concentrations. For a detailed look at how glycolic acid works at the cellular level, see our fundamentals guide.

Collagen Stimulation

Bernstein et al. (2001) demonstrated that topical application of 20% glycolic acid lotion for three months significantly increased type I collagen mRNA expression and hyaluronic acid content in human skin [7]. Kim et al. (1998) confirmed that glycolic acid stimulates greater collagen synthesis than other AHAs in dose-dependent fashion [8]. This evidence base for collagen stimulation has not been replicated with mandelic acid.

Hyperpigmentation

Glycolic acid addresses hyperpigmentation through two mechanisms: it accelerates cell turnover to disperse melanin deposits in the epidermis [1], and it directly inhibits tyrosinase activity to suppress melanin production [9]. For stubborn dark spots and melasma in people who tolerate it well, glycolic acid remains the most evidence-backed AHA option.

Acne Treatment

A large RCT (n=120) demonstrated that 10% glycolic acid applied daily significantly improved mild acne compared to placebo, with visible improvement by day 45 [10]. Glycolic acid also has pH-dependent antibacterial activity against Cutibacterium acnes at concentrations as low as 0.2% [11].

Mandelic Acid: Profile and Strengths

Mandelic acid is derived from bitter almonds (its name comes from the German Mandel, meaning almond). While it has less clinical research than glycolic acid, its unique combination of gentleness and partial lipophilicity has made it increasingly popular - particularly for skin types and concerns where glycolic acid's potency becomes a liability.

Gentleness and Tolerability

Mandelic acid's larger molecular size means it penetrates the stratum corneum significantly more slowly than glycolic acid at equivalent concentrations and pH values. This slower penetration translates directly to less acute irritation: less stinging on application, less redness, and less peeling during the initial adjustment period [4].

For people whose skin barrier is easily compromised - whether from rosacea tendencies, atopic history, or simply innate sensitivity - mandelic acid can deliver meaningful exfoliation without triggering the flare cycle that glycolic acid sometimes initiates. If you have experienced side effects from glycolic acid in the past, mandelic acid is worth considering.

Lipophilic Pore Penetration

This is mandelic acid's distinguishing feature. Unlike glycolic acid, lactic acid, and other water-soluble AHAs, mandelic acid can partially dissolve into the oily sebum inside pores [3]. This gives it a mechanism of action for comedonal acne (blackheads, whiteheads) that other AHAs simply cannot replicate.

The pore-penetrating ability is less complete than that of salicylic acid (BHA), but it is enough to make mandelic acid a meaningful option for acne treatment - particularly for patients who want an AHA-based approach or who react poorly to salicylic acid.

Suitability for Darker Skin Tones

Mandelic acid has gained particular attention for its suitability for Fitzpatrick skin types IV through VI. In melanin-rich skin, aggressive exfoliation can trigger post-inflammatory hyperpigmentation (PIH), where the treatment itself creates new dark spots - making the condition worse rather than better [12].

Mandelic acid's slower, gentler penetration significantly reduces this risk. Sarkar et al. (2012) identified mandelic acid as one of the safer peel options for darker skin in their comprehensive review of chemical peels for melasma [12]. Garg et al. (2009) compared glycolic acid peels to salicylic-mandelic acid peels in Indian skin types and found them equally effective for active acne and hyperpigmentation, but the salicylic-mandelic combination was better tolerated [13].

For detailed guidance on safe acid use for darker skin, see our melanin-rich skin guide.

Antibacterial Properties

Like glycolic acid, mandelic acid has demonstrated antibacterial activity. Its phenyl group structure is related to that of phenoxyethanol, a common antimicrobial preservative, and studies have shown mandelic acid has activity against several bacterial strains relevant to skin health [3]. This antibacterial effect, combined with its pore-penetrating ability, reinforces its role as an acne treatment.

Head-to-Head Comparison

For Anti-Aging

Winner: Glycolic acid.

The evidence for glycolic acid's collagen-stimulating and texture-improving properties is substantially stronger than for mandelic acid. Bernstein et al. (2001) demonstrated molecular-level changes (increased collagen mRNA and hyaluronic acid) with glycolic acid [7], and the 2025 network meta-analysis confirmed its efficacy for skin roughness reduction [6]. Mandelic acid has not been studied for anti-aging outcomes with comparable rigor. If photoaging, rough texture, or loss of firmness is your primary concern, glycolic acid is the evidence-backed choice.

Caveat: For fine wrinkle reduction specifically, retinoids remain superior to both AHAs [6].

For Acne

Nuanced - depends on your skin.

Glycolic acid has stronger RCT evidence for acne: a large placebo-controlled trial (n=120) demonstrated efficacy at 10% [10], and it has documented antibacterial activity against C. acnes [11]. A 2018 systematic review also supports chemical peels containing glycolic acid for acne vulgaris [14].

However, mandelic acid has a structural advantage: its partial lipophilicity allows it to penetrate into pores in a way glycolic acid cannot [3]. Garg et al. (2009) found salicylic-mandelic acid peels equally effective as glycolic acid peels for active acne, with better tolerability [13].

Choose glycolic acid if your skin tolerates it and you want the most evidence-backed approach. Choose mandelic acid if glycolic acid irritates your skin, if you have sensitive or dark skin, or if you want pore-level activity from an AHA rather than switching to a BHA.

For Hyperpigmentation

Glycolic acid is more potent, but mandelic acid is safer for dark skin.

Glycolic acid combines faster cell turnover with direct tyrosinase inhibition [9], giving it a meaningful advantage for dark spots and melasma in patients who tolerate it. A 2025 RCT found glycolic acid peels more effective than lactic acid peels for melasma [15], and glycolic acid peels have been used successfully for post-inflammatory hyperpigmentation in darker skin - though with careful protocols [16].

Mandelic acid addresses hyperpigmentation more gently, with lower risk of triggering new PIH in the process. For Fitzpatrick IV-VI skin tones, this safety advantage often outweighs glycolic acid's potency advantage - particularly for patients who have experienced PIH from previous treatments [12].

For Sensitive Skin

Winner: Mandelic acid.

If your skin is reactive, easily irritated, or has a history of adverse reactions to AHAs, mandelic acid is the safer choice. Its larger molecular size and slower penetration produce less acute irritation than glycolic acid at equivalent concentrations. The gentler penetration profile means less stinging, less redness, and a lower risk of the barrier disruption that can cascade into persistent sensitivity.

For more on adapting acid use to reactive skin, see our skin types guide.

For Darker Skin Tones

Winner: Mandelic acid.

This is where mandelic acid has its clearest advantage. In melanin-rich skin (Fitzpatrick IV-VI), the risk of post-inflammatory hyperpigmentation from aggressive exfoliation is a real clinical concern - not a theoretical one. Mandelic acid's gentler penetration profile reduces this risk substantially [12]. Glycolic acid can be used safely in darker skin types, but it requires careful protocols, gradual introduction, and professional oversight [16].

For a first-line AHA in darker skin, mandelic acid is the lower-risk choice. Patients can always progress to glycolic acid under professional guidance once they know their skin tolerates chemical exfoliation without PIH.

For Texture and Roughness

Winner: Glycolic acid.

This is glycolic acid's core strength. Its smaller molecular size allows more uniform and deeper penetration across the stratum corneum, producing smoother, more evenly exfoliated skin. For stubborn rough patches, keratosis pilaris, or overall dullness, glycolic acid delivers faster and more noticeable results [1]. Mandelic acid can improve texture over time but works more slowly and produces less dramatic resurfacing.

For Beginners

Winner: Mandelic acid.

If you have never used an AHA before and are uncertain how your skin will respond, mandelic acid is the lower-risk starting point. Its gentler penetration means less chance of the stinging, redness, and peeling that can discourage new AHA users. You can always progress to glycolic acid later once your skin has demonstrated it tolerates chemical exfoliation.

Concentration Ranges Compared

Both acids are available across a range of concentrations, but the effective ranges differ because of their different potencies.

Mandelic acid over-the-counter products typically range from 5% to 10%. At these concentrations, mandelic acid provides gentle exfoliation suitable for regular home use. Some products go up to 15%, though higher concentrations are less common than for glycolic acid.

Glycolic acid over-the-counter products typically range from 5% to 10%. The CIR Expert Panel has established 10% at pH 3.5 or higher as the upper safety limit for consumer cosmetic products in the US [17]. The EU is more conservative, limiting consumer leave-on products to 4% glycolic acid at pH 3.8 or higher [18].

For professional peels, glycolic acid concentrations range from 20% to 70%, while mandelic acid peels typically use 20% to 50%. Mandelic acid peels are often combined with salicylic acid (the "salicylic-mandelic" or SM peel) to leverage the complementary pore-penetrating abilities of both acids [13].

Remember that concentration alone does not determine potency. The pH of the product determines how much of the acid is in its active (non-ionized, or "free acid") form. Because mandelic acid has a lower pKa (3.41) than glycolic acid (3.83), a mandelic acid product at a given pH will have a slightly higher proportion of free acid - though its larger molecular size still results in gentler overall effects [19]. Use our free acid calculator to compare the actual potency of products.

Can You Use Both?

Yes. Glycolic acid and mandelic acid can be used in the same routine, either by alternating them or by using multi-acid formulations that contain both. Because they share the same fundamental mechanism of action (desmosome disruption), the primary risk of combining them is over-exfoliation, not chemical incompatibility.

Safe Approaches

Alternate products. Use a glycolic acid product on some evenings for deeper exfoliation and a mandelic acid product on others for gentler maintenance with pore-level activity. For example, glycolic acid 2 nights per week and mandelic acid 2-3 nights per week, with rest days in between.

Target different concerns. Use glycolic acid to address areas of stubborn texture or hyperpigmentation (forehead, chin) and mandelic acid on areas prone to acne or sensitivity (cheeks, jawline).

Multi-acid formulations. Some products combine glycolic and mandelic acid at lower individual concentrations, aiming to provide some of glycolic acid's penetration depth with mandelic acid's pore-level activity and gentleness.

Seasonal rotation. Use glycolic acid during cooler months when UV exposure is lower and transition to mandelic acid during summer for gentler exfoliation with less photosensitivity risk.

Use the interaction checker to verify that the acids in your routine are safe to combine with your other products.

How to Choose: Decision Framework

Choose glycolic acid if:

• Your primary concern is rough, uneven skin texture or dullness
• You want to address signs of photoaging (roughness, loss of radiance)
• You are dealing with stubborn hyperpigmentation or dark spots and your skin tolerates AHAs
• Your skin is normal to oily and not particularly sensitive
• You have used AHAs before and tolerate them well
• You want the most clinically studied AHA

Choose mandelic acid if:

• You have sensitive or reactive skin
• You have a darker skin tone (Fitzpatrick IV-VI) and want to minimize PIH risk
• You have acne-prone skin and want an AHA with pore-penetrating ability
• You are new to chemical exfoliation and want a gentle starting point
• You have experienced irritation from glycolic acid in the past
• You want the gentleness of a large AHA with some of the pore activity of a BHA

Choose both if:

• You want to alternate between deeper resurfacing (glycolic) and gentler pore-level exfoliation (mandelic)
• You have combination skin with different needs in different areas
• You are using a multi-acid formulation that combines both at lower concentrations

For a broader view of how glycolic acid compares across the entire AHA family, see our complete AHA comparison guide. To explore glycolic acid's differences from the other popular gentle AHA, see our glycolic acid vs lactic acid comparison.

Frequently Asked Questions

Is mandelic acid just a weaker version of glycolic acid?

No. Mandelic acid is gentler than glycolic acid, but "gentle" and "weak" are not the same thing. Mandelic acid has a unique property - partial lipophilicity - that glycolic acid lacks entirely. This allows mandelic acid to penetrate into pores, giving it a mechanism of action for acne that purely water-soluble AHAs cannot match [3]. For sensitive skin, acne-prone skin, and darker skin tones, mandelic acid is not an inferior choice - it is the more appropriate one.

Can I switch from mandelic acid to glycolic acid?

Yes. If you have been using mandelic acid and want to try glycolic acid for stronger resurfacing, reduce mandelic acid use for a few days, then introduce glycolic acid at the lowest available concentration (typically 5%) two to three times per week. Increase frequency gradually as tolerated. Your prior AHA experience means your skin has some baseline tolerance, but glycolic acid will feel more intense at first due to its faster, deeper penetration.

Is mandelic acid better than salicylic acid for acne?

They work differently. Salicylic acid (BHA) is fully lipophilic and penetrates deeply into pores, making it the most targeted option for comedonal acne [3]. Mandelic acid is only partially lipophilic, so its pore penetration is less complete. However, mandelic acid also provides surface exfoliation that salicylic acid does not, and it may be better tolerated by sensitive skin. For a full comparison between glycolic acid and salicylic acid, see our dedicated guide.

Which acid is better for melasma on dark skin?

For melasma specifically, glycolic acid has stronger efficacy evidence [15], but mandelic acid carries lower risk of triggering post-inflammatory hyperpigmentation in darker skin tones [12]. Many dermatologists start with mandelic acid in Fitzpatrick IV-VI patients to establish tolerance before considering glycolic acid. The safest approach depends on your specific skin tone, melasma severity, and history of PIH.

Do glycolic acid and mandelic acid have the same pH requirements?

Both follow the Henderson-Hasselbalch equation, but their pKa values differ: glycolic acid has a pKa of 3.83, while mandelic acid's pKa is 3.41 [19]. This means at the same pH, mandelic acid has a higher proportion of free (active) acid. A product pH of 3.0-4.0 is effective for both, but the free acid percentages will differ at each pH point. Learn more about pH science in skincare and use the free acid calculator to compare specific products.

References

1. 1. Sharad J (2013). Glycolic acid peel therapy - a current review. Clin Cosmet Investig Dermatolreview
2. 2. Van Scott EJ, Yu RJ (1974). Control of keratinization with alpha-hydroxy acids and related compounds. I. Topical treatment of ichthyotic disorders. Arch Dermatolclinical trial
3. 3. Green BA, Yu RJ, Van Scott EJ (2009). Clinical and cosmeceutical uses of hydroxyacids. Clin Dermatolreview
4. 4. Tang SC, Yang JH (2018). Dual Effects of Alpha-Hydroxy Acids on the Skin. Moleculesreview
5. 5. Fartasch M, Teal J, Menon GK (1997). Mode of action of glycolic acid on human stratum corneum: ultrastructural and functional evaluation of the epidermal barrier. Arch Dermatol Resclinical trial
6. 6. Sci Rep (2025). Comparative efficacy of topical interventions for facial photoaging: a network meta-analysis. Sci Repnetwork meta-analysis
7. 7. Bernstein EF, Lee J, Brown DB, et al. (2001). Glycolic acid treatment increases type I collagen mRNA and hyaluronic acid content of human skin. Dermatol Surgclinical trial
8. 8. Kim SJ, Park JH, Kim DH, Won YH, Maibach HI (1998). Increased in vivo collagen synthesis and in vitro cell proliferative effect of glycolic acid. Dermatol Surgclinical trial
9. 9. Usuki A, Ohashi A, Sato H, et al. (2003). The inhibitory effect of glycolic acid and lactic acid on melanin synthesis in melanoma cells. Exp Dermatolin vitro study
10. 10. Abels C, Kaszuba A, Michalak I, et al. (2011). A 10% glycolic acid containing oil-in-water emulsion improves mild acne: a randomized double-blind placebo-controlled trial. J Cosmet DermatolRCT
11. 11. Yang AJ, et al. (2020). pH-Dependent Antibacterial Activity of Glycolic Acid: Implications for Anti-Acne Formulations. Sci Repin vitro study
12. 12. Sarkar R, Garg S, Bansal S, Sethi S (2012). Chemical peels for melasma in dark-skinned patients. J Cutan Aesthet Surgreview
13. 13. Garg VK, Sinha S, Sarkar R (2009). Glycolic acid peels versus salicylic-mandelic acid peels in active acne vulgaris and post-acne scarring and hyperpigmentation: a comparative study. Dermatol Surgcomparative study
14. 14. Castillo DE, Yousef K (2018). Chemical peels for acne vulgaris: a systematic review of randomised controlled trials. BMJ Evidence-Based Medicinesystematic review
15. 15. Indian J Dermatol (2025). 80% Lactic Acid Peel Versus 50% Glycolic Acid Peel for Melasma: A Randomised Clinical Trial. Indian J DermatolRCT
16. 16. Burns RL, Prevost-Blank PL, Lawry MA, et al. (1997). Glycolic acid peels for postinflammatory hyperpigmentation in black patients. A comparative study. Dermatol Surgclinical trial
17. 17. Andersen FA (1998). Final Report on the Safety Assessment of Glycolic Acid. Int J Toxicolsafety assessment
18. 18. Scientific Committee on Consumer Safety (SCCS) (2000). Opinion on Alpha-Hydroxy Acids. SCCNFP/0370/00regulatory opinion
19. 19. Decker LC, Graber EM (1996). Clinical and histological effects of glycolic acid at different concentrations and pH levels. Dermatol Surgclinical trial
20. 20. Kaidbey K, Sutherland B, Bennett P, et al. (2003). Topical glycolic acid enhances photodamage by ultraviolet light. Photodermatol Photoimmunol Photomedclinical trial

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