Glycolic Acid (GA) is a naturally-derived ingredient used in skin care for exfoliation in the treatment of facial scarring, acne, pigmentation-related issues, and overall skin rejuvenation. It holds a strong and long-lasting reputation within the cosmetic industry for its efficacy and safety in application, despite its ability to penetrate well into the epidermis.
Originally obtained from sugarcane, Glycolic Acid is the smallest of the alpha-hydroxy acid group,1 a group of acids derived from fruits that also contain other well-known ingredients such as Lactic Acid.
Alpha-hydroxy acids have reached renown within acne treatments for their ability to moderate excess skin-production, treat epidermal issues (like superficial scarring and pigmentation), and to increase collagen within the skin for improved elasticity.2
Glycolic Acid, as the smallest alpha-hydroxy, contains smaller molecules than any of the other acids within its group, and as such can go deeper into the epidermis to treat acne scars with more localization and efficacy.2 Due to its gentler nature than more intensive acne-treatment ingredients, like Benzoyl Peroxide, it is regularly used for those with sensitive skin or with higher risk for hyperpigmentation following other treatments.2
GA is also an antioxidant,2 contains bactericidal properties that help to kill the bacteria responsible for acne (propionibacterium acne),3 and is hydrophilic in nature (which allows it to penetrate the water barrier of skin cells).2 This creates an exfoliative property for Glycolic Acid which allows it to thin the outer layer of the skin in order to disperse melanin, create a thicker epidermis, and restore skin texture.3
Glycolic Acid’s role as an exfoliating agent is defined by its ability to deconstruct the epidermis and reduce protein buildups (such as in blackheads and acne), create the reduction of pustules and papules (infected and inflamed skin), and compliment the restoration of fibers following the controlled destruction of certain areas of the skin.4
This exfoliating property allows GA to effectively target superficial and medium-depth issues of the epidermis with a high efficacy, allowing natural healing to occur at the point of penetration. This enables a renewal of healthier and replenished skin tissue, which addresses many issues related to scarring, texture, and aging.4
This is accomplished through the low pH of alpha-hydroxy acids, as they are able to increase transmembrane permeability in cells (which weakens the cell barrier).5 The newly fragile barrier enables GA to force the mobilization of epithelial cells to repair and replace damaged skin, as it uses epidermolysis (a temporary loosening of the skin to force healing) on the old/deteriorated skin.4
The acidic nature of GA helps it to rejuvenate skin once entering the epidermis by reducing follicular pores, acne-scarring, melanosis, and the development of new acne lesions.4 Despite these acidic properties of GA, it is also an anti-inflammatory and positively treats inflamed areas of the skin (such as acne lesions) with a high efficacy — helping to prevent post-inflammatory hyperpigmentation following the controlled removal of the treated skin.4
The actual mechanism that helps to treat skin and pigment issues is referred to as epidermal remodeling and/or desquamation (skin peeling) which allows Glycolic Acid to force the healing factor of the skin to begin, and replenishes the old or damaged areas of the epidermis with newly-renewed skin.6 This ability disperses melanin/pigment in areas of sun damage, or those suffering from post-acne hyperpigmentation, and restores collagen and elasticity in the affected areas.5
Glycolic Acid is primarily used to target issues such as: acne/acne scars, post-inflammatory hyperpigmentation, melasma, dry skin, and fine-lines/wrinkling. In the treatment of acne, the direct effect of GA’s bactericidal properties on propionibacterium acne provides a large part of its treatment abilities for both inflammatory and non-inflammatory acne.3
Clinical studies, which follow GA’s efficacy for acne treatment, have concluded that there is a significant reduction in the reproduction of new acne spots and a high ability to treat blackheads and inflamed acne following its use for exfoliation.3,7,8 Along with its ability to cleanse pores, it is also able to increase the absorption of other topical agents used for acne — allowing even further healing when used in conjunction with other ingredients.7
Beyond its uses in the treatment of acne, Glycolic Acid is used to treat the aftereffects of acne and sun damage. Both commonly result in pigment and texture issues within the skin, such as: post-inflammatory hyperpigmentation, melasma, and acne scars.
Post-inflammatory hyperpigmentation (PIH) follows the over-production of melanin and/or an irregular dispersion of pigment that is most commonly associated with any type of skin infection, or the other major sources of inflammation (sun damage, dry skin, etc.).9 Melasma is referred to when PIH is a result of sun damage specifically, but both are a result of too much melanin within the epidermal and dermal cells.
Glycolic Acid has been proven to assist with PIH and melasma through its ability to disperse melanin during the exfoliation process, and inhibits the tyrosinase enzyme responsible for melanin’s production.6 Its use as an exfoliant in the treatment of PIH and melasma is clinically proven to result in new and less-pigmented skin with renewed texture.4,6,8,9
The replenishing factor of Glycolic Acid also helps to treat issues such as dry skin, acne-scarring, and fine-lines/wrinkles due to renewed collagen within the skin. This is accomplished through the reduction of follicular pores, protein build-ups, and inflammation as GA is applied.2
After application, newer and more elastic skin becomes evident and certain skin fibers (that are damaged during the aging process, acne, and/or sun damage) are able to be effectively targeted and healed, up to a certain extent.4
The ability to exfoliate and replenish skin, reduce inflammation, and inhibit melanin production reduces most major contributory issues for texture and pigment, which has led Glycolic Acid to be regularly employed and studied for the treatment of many skin disorders — with all studies of its efficacy concluding highly promising results.2,4,6,9,10
The best results for Glycolic Acid strongly depend on its mode of application, condition it is being used to treat, and concentration in the specific product it is contained within.
As an example, chemical peels (performed by professionals in certified clinics) have been observed to be most-effectively used for five sequential treatments every two weeks at a concentration of 70%,5 but typical home-use applications are generally used once each day. This means it is important to follow the application instructions on the product that is to be used.
As the results can vary in efficacy and time depending on the modality of treatment and severity of condition, timelines can be difficult to establish on a continuous basis; however, some studies have noticed demonstrable results at the twelve-week mark in the improvement of acne, scarring, pigmentation, and texture.4,6
Although this twelve-week point may have come up in multiple studies, the product provider and instructions should be followed in order to achieve the best results for the chosen concentration of Glycolic Acid.
The side-effects of Glycolic Acid are explored regularly through clinical studies, and have been proven to not be very significant or lasting in effect, with the large majority of patients not experiencing any.2,3,4,5,8
Glycolic Acid is concluded to be one of the most reliable ingredients to use as an exfoliant or through topical application, and is regularly employed for those with safety concerns due to its wide versatility and ability to penetrate the epidermis without (aside from rare cases) side-effects.2
Glycolic Acid is often compared to other alpha-hydroxy acids like Lactic, and other treatments for pigment and texture such as Vitamin C, Hyaluronic Acid, and Salicylic Acid. As the properties of each are different, it can heavily affect what they are being used to treat, and their comparison is done in respect to certain conditions.
Vitamin C overlaps most heavily with Glycolic Acid as an antioxidant and treatment for pigmentary issues within the skin, but Vitamin C is a more-targeted ingredient for hyperpigmentation and UV protection compared to GA; conversely, Glycolic Acid is mainly used as an acne treatment (so a combination of the two is most likely to lead to the highest skin-care benefits).11
Hyaluronic Acid (HA) is a complex type of acid that exists within the dermis and epidermis, and is responsible for hydration within the majority of mammals. When applied topically, it is able to restore moisture to the skin (resulting in a plumping/firming effect) and can effectively treat dry skin.12 This application is different than Glycolic Acid’s primary use of exfoliation, and the combination of these two acids is extremely beneficial in cleaning and hydrating skin.
However, GA (due to its smaller molecules) is a gentler solution for the penetration of the skin and is better suited for treating acne and exfoliation, due to its smaller molecule size and ability to act as an anti-inflammatory.4
Salicylic Acid (SA) is a beta-hydroxy acid, making it a different type of acid than Glycolic Acid; this differentiation in acid-type indicates SA is able to penetrate lipid (oily) barriers in cells due to the lipophilic properties of beta-hydroxy acids — while GA (an alpha-hydroxy) is water-soluble, so it is unable to pass through those same oily barriers.. This provides a key difference between Glycolic Acid and SA, as beyond the epidermis (into the dermis) there is an increasing difficulty in permeability, and GA is not able to penetrate these due to its inability to pass through oils/fats in the cells.2,3
For the treatment of comedones (blackheads) and dermal (as opposed to epidermal) melasma, Salicylic Acid is proven to be more effective due to its lipophilic nature, but as it penetrates deeper into the skin, it is more ideal from those with deep-scarring or specific types of acne.2,3 Glycolic Acid is better suited to superficial active and inflamed acne lesions (pustules), while Salicylic is better for closed off/oily pores (blackheads).
Lactic Acid (LA) is another alpha-hydroxy acid, found in sour milk and bilberries, and is extremely similar to Glycolic Acid in both treatment use and penetrative ability.3 They share the ability to cause epidermolysis (the regeneration of skin) during exfoliation, target acne-prone molecules, and lighten areas suffering from pigment issues.3,11
In comparison, Glycolic Acid (due to its smaller size) is able to target microfibers within the skin with more accuracy, but degrades the fibers more slowly than LA due to its smaller molecular weight.13 This means that Lactic Acid is more likely to show results quickly, but does not share the same micro-penetration that Glycolic Acid is able to achieve.
1. Khee, H. J., May, L. M., Sam, Y. S., Derrick, A. C. W., & Sue-Ann, H. (2017). The efficacy and safety of a 70% glycolic acid peel with vitamin C for the treatment of acne scars. Journal of Surgical Dermatology, 2(4), 209-213.
2. Sarkar, R., Garg, V., Bansal, S., Sethi, S., & Gupta, C. (2016). Comparative evaluation of efficacy and tolerability of glycolic acid, salicylic mandelic acid, and phytic acid combination peels in melasma. Dermatologic Surgery, 42(3), 384-391.
3. Castillo, D. E., & Keri, J. E. (2018). Chemical peels in the treatment of acne: patient selection and perspectives. Clinical, cosmetic and investigational dermatology, 11, 365.
4. WANG, C. M., HUANG, C. L., SINDY HU, C. T., & CHAN, H. L. (1997). The effect of glycolic acid on the treatment of acne in Asian skin. Dermatologic surgery, 23(1), 23-29.
5. Fabbrocini, G., Annunziata, M. C., D’arco, V., De Vita, V., Lodi, G., Mauriello, M. C., … & Monfrecola, G. (2010). Acne scars: pathogenesis, classification and treatment. Dermatology research and practice, 2010.
6. Chandrashekar, B. S., Ashwini, K. R., Vasanth, V., & Navale, S. (2015). Retinoic acid and glycolic acid combination in the treatment of acne scars. Indian dermatology online journal, 6(2), 84.
7. Govindarajan, N. (2018). A comparative study of the resurfacing effect of microdermabrasion versus glycolic acid peel in the management of acne scars. Journal of Pakistan Association of Dermatology, 28(2), 224-232.
8. Chien, A. L., Qi, J., Rainer, B., Sachs, D. L., & Helfrich, Y. R. (2016). Treatment of acne in pregnancy. J Am Board Fam Med, 29(2), 254-262.
9. Rosario, A. M., & Monteiro, R. (2015). A comparative study to assess the safety and efficacy of 12% glycolic acid v/s 10% azelaic acid in the treatment of post acne hyperpigmentation. Int J Sci Res Publ, 5, 25-34.
10. Sarkar, R., Garg, V., Bansal, S., Sethi, S., & Gupta, C. (2016). Comparative evaluation of efficacy and tolerability of glycolic acid, salicylic mandelic acid, and phytic acid combination peels in melasma. Dermatologic Surgery, 42(3), 384-391.
11. Tran, D., Townley, J. P., Barnes, T. M., & Greive, K. A. (2015). An antiaging skin care system containing alpha hydroxy acids and vitamins improves the biomechanical parameters of facial skin. Clinical, cosmetic and investigational dermatology, 8, 9.
12. Rivera, A. E. (2008). Acne scarring: a review and current treatment modalities. Journal of the American Academy of Dermatology, 59(4), 659-676.
13. Li, S. (1999). Hydrolytic degradation characteristics of aliphatic polyesters derived from lactic and glycolic acids. Journal of Biomedical Materials Research: An Official Journal of The Society for Biomaterials, The Japanese Society for Biomaterials, and The Australian Society for Biomaterials, 48(3), 342-353.