IngredientsGlycolic acid (also known as hydroxyacetic acid; chemical formula HOCH2CO2H) is a colorless, odorless, and hygroscopic crystalline solid that is highly soluble in water. Its IUPAC chemical name is 2-hydroxyethanoic acid, and its CAS number is 79-14-1. It is an alpha hydroxy acid (AHA), containing both a carboxylic acid group and a hydroxyl group separated by a single carbon atom. A glycolate is a salt or ester of glycolic acid.
Glycolic acid is the smallest molecule among the alpha hydroxy acids, a structural feature with significant implications for its pharmacological behavior. It is slightly stronger than acetic acid due to the electron-withdrawing power of the terminal hydroxyl group.
Glycolic acid can be isolated from natural sources such as sugarcane, sugar beets, pineapple, cantaloupe, and unripe grapes. Sugar cane is the primary source because it yields the highest concentration of glycolic acid, making the extraction process more efficient. Glycolic acid can also be naturally produced in small amounts via the reduction of glyoxylate in bacteria and moulds, including yeast.
The name "glycolic acid" was coined in 1848 by French chemist Auguste Laurent (1807–1853), who proposed that the amino acid glycine — then called glycocolle — might be the amine of a hypothetical acid, which he termed acide glycolique. Glycolic acid was first formally prepared in 1851 by German chemist Adolph Strecker and Russian chemist Nikolai Nikolaevich Sokolov, who produced it by treating hippuric acid with nitric acid and nitrogen dioxide to form an ester of benzoic acid and glycolic acid, which they termed "benzoglycolic acid."
Glycolic acid is available in skin care and cosmetic products. Industrially, it is primarily produced by synthetic chemical processes rather than extraction from plant sources, owing to the high plant material volumes required for extraction. Glycolic acid can also be prepared using an enzymatic biochemical process that may require less energy. Common dosage forms include: aqueous gels and solutions for professional chemical peels (ranging from 20% to 70%); leave-on creams, serums, and lotions for consumer use (typically 5%–20%); toners, exfoliating pads, and wash-off cleansers at lower concentrations (2%–10%); and as a crystalline solid or concentrated aqueous solution in pharmaceutical and industrial grades.
The use of glycolic acid and other AHAs dates back to ancient times, with historical records indicating that ancient civilizations used natural sources of these acids, such as milk and fruits, for skin care. However, it is important to note that the use of glycolic acid itself for skin treatment does not have "traditional uses" in the historical or ancient sense, as its utilization in skincare is relatively modern; the longer history belongs to naturally occurring AHAs more broadly.
The compound's modern dermatological application began in the late 20th century. Glycolic acid is the most commonly used alpha-hydroxy acid for dermatologic applications and is considered a versatile superficial peeling agent for facial rejuvenation. Its rise in clinical dermatology is documented from the early 1990s, when researchers such as Murad described it as an agent to loosen bonds between dead and live skin cell layers. What was once a product used in medispas as part of routine aesthetic medical procedures, glycolic acid is now found in many at-home products.
As a discrete pure organic acid, glycolic acid is itself the sole active constituent rather than containing multiple secondary compounds. Its pharmacological activity is a direct consequence of its chemical structure. The relevant chemical characteristics include:
When AHAs are applied to the skin, they can cause the top layer of dead skin cells to detach from each other and fall off (exfoliation). Getting rid of dead skin cells can improve the appearance of the skin and increase how quickly new skin cells grow to replace old cells. Glycolic acid's therapeutic effect includes acceleration of epidermal turnover without apparent inflammation, and its action is pH-dependent.
At the molecular level, research has identified a role for transient receptor potential (TRP) channels. After GA application, BrdU incorporation into basal keratinocytes was significantly increased. Induction of keratinocyte proliferation was pH-dependent and was inhibited by antagonists of TRPV1, an acid-sensitive ion channel. Furthermore, transient ATP release was detected in culture medium after GA stimulation, and this was also suppressed by TRPV1 antagonists. These results suggest that one of the mechanisms of GA-induced epidermal proliferation is a growth response of basal keratinocytes to the local elevation of H⁺-ion concentration by infiltrated GA, mediated by TRPV1 activation and ATP release; activation of P2 receptors by the released ATP may also be involved.
An in vitro and ex vivo study investigated the effect of GA on the dermal matrix metabolism of keratinocytes and fibroblasts. The study showed that GA not only directly accelerates collagen synthesis by fibroblasts, but also modulates matrix degradation and collagen synthesis through keratinocyte-released cytokines. IL-1α was confirmed as one of the primary mediators for matrix degradation released from keratinocytes after GA treatment, suggesting that GA contributes to recovery of photodamaged skin through various actions, depending on the skin cell type.
A separate skin explant study confirmed these findings: stimulation of keratinocyte proliferation was observed upon GA treatment and was concentration-dependent up to 15%; the study demonstrated that GA at these concentrations increased dermal collagen levels, and this effect was largely concentration dependent. In vitro results show that glycolic acid caused elevated collagen production in fibroblasts, demonstrating a specific stimulatory effect that could explain some of the positive benefits from its clinical use.
AHAs, including glycolic acid, can help attract water to the skin, increasing skin hydration. This hygroscopic effect is partly responsible for the improvement in skin texture and softness observed with regular low-concentration use.
At lower concentrations, preclinical data show a potential anti-inflammatory role. GA inhibited the UVB-induced promoter activity of NF-κB in HaCaT cells; topical GA inhibited gene expression of IL-1β, IL-6, IL-8, COX-2, and MCP-1 in UVB-exposed mouse skin; mice exposed to UVB after GA was topically applied for 9 consecutive days showed that 1–1.5% GA exerted anti-inflammatory effects on mouse skin. This mechanism has been characterized only in cell-culture and murine models and has not been confirmed in prospective human clinical trials.
GA has both bacteriostatic and bactericidal effects on Propionibacterium acnes, a bacterium associated with acne. This antimicrobial effect complements its keratolytic action in acne management, though the relative contribution of this mechanism in vivo remains to be clarified by dedicated human studies.
High-concentration peels (50%): A double-blind, vehicle-controlled study in 41 volunteers applied 50% glycolic acid or vehicle to one side of the face, forearms, and hands, once weekly for 4 weeks. Results showed significant improvement including decrease in rough texture and fine wrinkling, fewer solar keratoses, and a slight lightening of solar lentigines; histology showed thinning of the stratum corneum, granular layer enhancement, and epidermal thickening.
Low-concentration creams (8%): A 22-week, double-blind, vehicle-controlled randomized clinical trial at Massachusetts General Hospital enrolled 74 women, aged 40–70 years, with moderately severe photodamaged facial skin, applying glycolic acid or vehicle twice daily to the face and forearms. The percentage of patients using 8% glycolic acid cream on the face achieving at least 1 grade of improvement in overall severity of photodamage was significantly greater than with vehicle (76% glycolic acid vs. 40% vehicle; P < .05); on the forearms, treatment with glycolic acid cream was superior to vehicle in improving overall severity of photodamage and sallowness (P < .05). Topical 8% glycolic acid and 8% L-lactic acid creams were found modestly useful in ameliorating some of the signs of chronic cutaneous photodamage and were well tolerated.
Low-concentration creams (5%): In a double-blind, randomized, placebo-controlled trial in 75 volunteers, participants applied either 5% glycolic acid cream or placebo cream to the face and neck for a period of 3 months, with pre- and post-treatment clinical assessments of photoaging. Overall there were trends toward greater improvement in the glycolic acid group for all clinical assessments for photoaging; there was statistically significant improvement favoring the active cream in general skin texture and discoloration; however, there was only a trend favoring glycolic acid in reduction of wrinkles, which did not achieve statistical significance.
Network meta-analysis: A 2025 systematic review and network meta-analysis in Scientific Reports identified 23 RCTs with 3,905 participants comparing anti-aging agents. Bayesian network meta-analysis showed isotretinoin, retinol, and tretinoin significantly improved fine wrinkles, with isotretinoin ranked highest; tazarotene was most effective for coarse wrinkles, while glycolic acid reduced roughness; tretinoin and retinol were superior for hyperpigmentation. Glycolic acid did not achieve a statistically significant result for improving fine wrinkles, indicating that further validation is required. Safety analysis indicated that glycolic acid had higher adverse event risks compared to tretinoin in this comparative analysis.
Evidence assessment: There is moderate clinical evidence, from multiple randomized controlled trials, that topical glycolic acid improves skin texture, sallowness, and photodamage. Evidence for wrinkle reduction specifically is less robust, and glycolic acid appears inferior to retinoids for fine wrinkles in network comparisons.
A prospective, randomized, double-blind, placebo-controlled, split-face clinical trial of 26 patients with moderate acne were treated with 40% GA (pH 2.0) on half of the face and placebo on the other half; the procedure was performed five times at 2-week intervals. The GA sides had statistically significant reductions in acne lesions at each time point from baseline values, with statistically significant differences between the GA and placebo sides; GA sides had better responses for non-inflammatory lesions than for inflammatory lesions.
A 2024 expert consensus publication in the International Journal of Dermatology and Venereology concluded: studies have demonstrated that GA at concentrations of 20%–70% (or ≤50%), at intervals of 2–4 weeks, is effective for mild to moderate acne, including comedones, papules, and pustules; GA has been shown to be more effective for comedones, whereas the effects of salicylic acid tend to be more long-lasting; both GA and SA peels are considered safe and well-tolerated.
A comparative study of 50% glycolic acid peel versus 30% salicylic acid peel in a randomized controlled trial of 50 participants with mild to moderate acne, randomly assigned to receive either 30% SA peel or 50% GA peel at two-week intervals for five sessions, found that patients in both groups demonstrated significant reductions in acne at the end of treatment.
Evidence assessment: Multiple randomized, controlled, split-face and comparative trials support the efficacy of glycolic acid peels for mild-to-moderate acne, particularly comedonal lesions. The evidence is moderate-to-good in strength for peels in the 20%–70% concentration range. Evidence for low-concentration daily products is limited.
A prospective, randomized, controlled trial enrolled 28 patients with recalcitrant melasma; patients in the peel group underwent serial glycolic acid peels in combination with topical azelaic acid 20% cream (b.i.d.) and adapalene 0.1% gel (applied at night). The results showed a prominent decrease in MASI scores at the end of treatment in both groups, although the results were better in the group receiving chemical peels.
In patients with refractory melasma not responding to topical tretinoin alone, a modified regimen using 20% glycolic acid and 5% hydroquinone twice daily resulted in excellent clearance of hyperpigmentation in all 7 enrolled patients two months later, confirmed by skin biopsy.
However, an evidence-based review published in PMC cited a Cochrane analysis finding that a Cochrane review could not find any benefit of adding GA peel to a combination of hydroquinone and glycolic acid cream. The same review concluded: all peels may be used in melasma with only mild to moderate efficacy expected, and there is no significant advantage of one peel over another.
A retrospective review of sequential high-concentration glycolic acid and trichloroacetic acid peels in 40 patients with Fitzpatrick skin phototypes IV–VI found: at 12 weeks, modified Melasma Area and Severity Index scores showed statistically significant improvement. The most common adverse effects were irritation (77.5%), post-peel cracking (62.5%), and transient hyperpigmentation (12.5%), with no cases of scarring observed. Critically, the recurrence rate of melasma reached 70% by week 12 after treatment cessation; the retrospective nature and single-center setting necessitate further prospective randomized controlled studies.
Evidence assessment: Glycolic acid peels show moderate efficacy for melasma as part of combination regimens; evidence for monotherapy is mixed. High recurrence rates after cessation of treatment are a consistent finding. Evidence strength is moderate but limited by study quality and high recurrence.
In a study by Burns et al., dark-skinned patients who received glycolic acid chemical peels showed rapid and greater improvement compared with the control group. Glycolic acid promotes epidermal exfoliation, enhances collagen synthesis, and improves post-inflammatory hyperpigmentation; a comparative study of 30% salicylic acid peel and 50% glycolic acid peel in mild to moderate acne vulgaris demonstrated that both chemical peeling agents are effective in treating acne, hyperpigmentation, and scarring.
Evidence assessment: Evidence for PIH improvement is largely from comparative and observational studies; controlled trial data are limited. Caution in darker skin phototypes is warranted given the risk of treatment-induced PIH.
A clinical study published in the World Journal of Clinical Cases (2021) evaluated a high concentration of glycolic acid in 25 participants with confirmed keratosis pilaris. A high concentration of glycolic acid significantly improved skin roughness as well as follicular hyperpigmentation of patients with keratosis pilaris; the treatment was relatively safe, but there was no significant difference at the 5-year follow-up compared to before treatment.
Glycolic acid can correct the abnormalities of hair follicular duct keratosis and eliminate excessive accumulation of keratinocytes; it also promotes skin metabolism and accelerates melanin metabolism; the therapeutic effect is related to the glycolic acid concentration.
More broadly, for most KP treatments, data exist only in the form of small group observations and anecdotal reports; one difficulty with evaluating the effectiveness of various KP therapies is that there is no validated assessment tool for this condition, and the methods employed to evaluate KP in clinical trials have been subjective, unreliable, and inconsistent.
Evidence assessment: Evidence is preliminary and based on small, uncontrolled or poorly validated studies. A lack of standardized outcome measures limits conclusions. Glycolic acid appears to offer short-term cosmetic improvement for KP but durability beyond the treatment period is not established.
Glycolic acid's documented clinical applications are essentially confined to the integumentary system — the skin and its appendages. The primary areas include:
There is no credible published clinical evidence for systemic (oral or injectable) effects of glycolic acid used as a dietary supplement or in any non-topical context. All peer-reviewed human evidence relates exclusively to topical dermatological application.
Glycolic acid is applied to the skin in a wide range of concentrations, usually from 5% to 70%.
Regarding pH as a critical variable: glycolic acid's efficacy and safety are concentration- and pH-dependent. The 2021 skin explant study demonstrated collagen-stimulating effects at pH 4, and the acne peel study specified use at pH 2.0. The Cosmetic Ingredient Review (CIR) has made concentration and pH recommendations discussed below.
Glycolic acid (10%) increases the UV-sensitivity of human skin; the photosensitizing effects of glycolic acid are small but may be important from the viewpoint of public health, considering that HA-containing products are being used by a large segment of the population for many years and in many cases over a lifetime.
The FDA has considered evidence that topically applied cosmetic products containing AHAs may increase the sensitivity of skin to the sun while the products are used and for up to a week after use is stopped, and that this increased skin sensitivity may increase the possibility of sunburn.
In a collaborative study with the National Toxicology Program, the FDA determined that glycolic acid did not affect photocarcinogenesis (the development of cancer cells associated with exposure to light) in mice. Nevertheless, human clinical studies found that topical application of glycolic acid at concentrations as low as 4% increased UV-induced sunburn cell formation or decreased minimal erythema dose.
Common side effects include redness, itching, irritation, peeling, stinging, or burning. Glycolic acid will also make skin more sensitive to sunlight. Serious side effects are uncommon but more likely with higher concentrations, and include rashes, burns, blisters, or infections.
The risk of adverse effects from glycolic acid is directly related to two factors: concentration and pH. As the concentration of glycolic acid increases, so does the risk of side effects; lower concentrations may cause mild skin irritation, while higher concentrations may cause redness, itching, burning, stinging, and blistering.
The Cosmetic Ingredient Review (CIR) published findings recommending that cosmetic products contain no more than 10.0% w/w glycolic acid and its derivatives and that the pH of any product be greater than 3.5; salon products should contain no more than 30.0% w/w glycolic acid and its derivatives and the pH of any product should be greater than 3.0.
The FDA recommended that the labeling of a cosmetic product containing an AHA as an ingredient, applied topically to the skin or mucous membrane, bear a statement conveying: "Sunburn Alert: This product contains an alpha hydroxy acid (AHA) that may increase your skin's sensitivity to the sun and particularly the possibility of sunburn."
Individuals with a naturally darker skin tone should speak to a health care provider before using glycolic acid due to the documented risk of treatment-induced post-inflammatory hyperpigmentation. Retrospective data in Fitzpatrick phototypes IV–VI reported transient hyperpigmentation in 12.5% of cases following sequential high-concentration peel protocols.
Isotretinoin dramatically thins the skin and impairs barrier function; using glycolic acid during or shortly after isotretinoin treatment creates a high risk of severe irritation, chemical burns, and scarring.
No large-scale pharmacokinetic drug interaction studies exist for glycolic acid with oral medications. Topical combination with other exfoliants (e.g., salicylic acid, benzoyl peroxide) and retinoids increases the risk of barrier disruption and irritation. The FDA has not formally reviewed glycolic acid for safety and effectiveness as a drug. Glycolic acid is available in skin care and cosmetic products; the FDA has not reviewed glycolic acid for safety and effectiveness as a drug under New Drug Application procedures.
Despite improvements during active treatment, the recurrence rate of melasma reached 70% by week 12 after treatment cessation, indicating that glycolic acid does not address the underlying chronicity of melasma and that ongoing maintenance strategies are required.
Health conditions that Glycolic acid may help support.
Glycolic acid is an alpha hydroxy acid used clinically for atrophic scar improvement, working by promoting exfoliation and stimulating collagen production. It is cited in evidence-based dermatological reviews as effective for textural improvement of atrophic scars including acne scars.
Glycolic acid, the simplest alpha-hydroxy acid (AHA), is a well-established cosmeceutical for photoaging and wrinkles. A 2025 Bayesian network meta-analysis of 23 RCTs (n=3,905) confirmed that glycolic acid significantly reduced skin roughness in photoaging. It promotes collagen synthesis, enhances exfoliation, and thickens the viable epidermis.
Body systems that Glycolic acid may help support.
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