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How Glycolic Acid Helps with Acne

Glycolic Acid Exfoliates the Skin, Decreases Skin Oil, Reduces Bacteria, Decreases Hyperpigmentation, and Promotes the Penetration of Acne Medications

By: Dan Kern, Acne.org Founder & CSO
Last updated: February 08, 2020

The Essential Information

Glycolic acid is an alpha hydroxy acid (AHA) that is used to treat a variety of skin conditions, including acne. It works by:

  • Exfoliating the skin
  • Decreasing sebum (skin oil)
  • Reducing bacteria
  • Decreasing hyperpigmentation
  • Promoting the penetration of acne medications
  • (unrelated to acne) Reducing signs of skin aging
     

Glycolic acid treatments come as over-the-counter products and professionally-administered chemical peels. Over-the-counter products can contain up to 10% glycolic acid, but higher concentrations, from 10 - 70%, must be applied by a skin care professional.

While glycolic acid is a very welcome adjunct to acne therapy, it will not clear the skin on its own, so it should be combined with other treatments for best results.

The side effects of glycolic acid are generally mild, and include mild stinging, burning, and itching, but high concentrations administered in doctors' offices and estheticians' salons can cause more severe side effects.

The Science

Introduction to Glycolic Acid

Glycolic acid is an alpha hydroxy acid (AHA), which is a type of acid used to treat a variety of skin conditions, including acne, ichthyosis, keratosis, warts, psoriasis, and sun-damaged skin. Glycolic acid is the most common AHA used to treat acne, as it was the first AHA scientists discovered, has the most scientific evidence behind it, and is easy to produce. Although it is found naturally in fruits, the glycolic acid used to treat skin diseases is almost always synthetically created in the laboratory in concentrations ranging from 2 - 70%, with over-the-counter products containing up to 10%. Glycolic acid is effective at clearing acne to some degree but is most effective when used in combination with acne medications instead of as a stand-alone treatment.1,2

Chemical Structure of Glycolic Acid

How Glycolic Acid Works to Clear Acne

Acne is a disease that results from skin pores becoming clogged with skin oil and dead skin cells. In normal, healthy skin, there is a constant process of skin renewal, where old, dead skin cells flake off the skin and are replaced with new ones. In acne, this process becomes disturbed, and old, dead skin cells accumulate instead of flaking off. The accumulation of these skin cells results in clogged pores, which can then lead to the development of inflammatory acne lesions.

Glycolic acid has several beneficial effects on acne and the skin in general.

Effects on acne

  • Exfoliates the skin: The accumulation of dead skin cells on the surface of the skin causes clogged pores and acne. Exfoliation of the skin can thin this layer of dead skin cells, which can help unclog pores that would otherwise develop into comedones (non-inflammatory acne) and potentially more severe forms of acne. Glycolic acids work to exfoliate the skin by:
     
    • Absorbing calcium: Glycolic acid can capture calcium particles. Calcium is an important mineral that binds to the surface of skin cells and helps the cell attach to other cells. Glycolic acid absorbs this calcium so that the calcium is not available to bind to skin cells. This weakens the connections between skin cells, and this helps to exfoliate the skin.
    • Breaking down keratin: Skin cells known as keratinocytes produce a "sticky" protein, called keratin. Keratin causes skin cells to stick together, and this results in them accumulating on the surface of the skin. Acne-prone individuals often produce more keratinocytes than non-acne-prone individuals, and this leads to more keratin and thus clogged pores and acne. Glycolic acid can break down keratin and "pull apart" skin cells that are stuck together, which helps to clear accumulated cells from the surface of the skin.
    • Breaking down surface skin cells: Corneocytes are a type of skin cell that makes up the top most layer of skin, called the stratum corneum. Glycolic acid promotes the breakdown of corneocytes, and therefore promote the thinning of the top layer of skin. Removing the corneocytes helps to exfoliate the skin, resulting in fewer clogged pores and less acne.
  • Decreases skin oil: Normally, the skin produces skin oil, called sebum, that helps to keep the skin healthy and protected. Acne-prone individuals often produce too much sebum, which can accumulate inside of a clogged pore and cause acne. Glycolic acid can decrease the amount of sebum the skin produces, which would help to prevent the formation of comedones.
  • Reduces bacteria: A bacteria called P. acnes thrives inside a clogged pore and can rapidly grow inside an acne lesion. This bacteria can make acne worse by initiating inflammation, that can make the lesion red, swollen, and sore. This bacteria can also trigger the development of pus. Glycolic acid possesses anti-bacterial properties, meaning that it can decrease the amount of P. acnes inside acne lesions.
  • Decreases hyperpigmentation: After an acne lesion heals, it leaves behind red/dark marks. Dermatologists call these marks post-inflammatory hyperpigmentation, or just hyperpigmentation for short. Hyperpigmentation is more common in people with non-Caucasian skin. Glycolic acid can decrease hyperpigmentation by stimulating the growth of new skin cells. Skin discoloration decreases because new skin cells rapidly replace the old, discolored cells, which evens out the color of the skin.
  • Promotes penetration of acne medications: To be effective at clearing acne, topical acne medications need to penetrate into the skin. A layer of accumulated dead skin cells covering the skin's surface can prevent medications from penetrating into the skin, which would decrease their effectiveness. Glycolic acid exfoliates the topmost layer of skin, and this allows for topical acne medications to seep into the skin more easily, improving their effectiveness.
  • Reduces scars: Severe acne lesions often leave scars. High-percentage glycolic acid peels can help somewhat reduce scarring from acne lesions.2-6

How Glycolic Acid Helps Acne

Effects on skin in general

  • Anti-aging: Glycolic acid has anti-aging properties, which means that it promotes:
     
    • Skin thickening: In healthy skin, collagen provides support and structure to the skin. If this collagen is damaged, or if the amount of collagen decreases, wrinkles form. Glycolic acid can increase the amount of collagen, which would help the skin maintain its shape and strength.
    • Skin hydration: Healthy skin must contain a certain amount of water, and without a proper level of water, it can become dry and flaky. This dryness can lead to skin damage and skin aging. Glycolic acid works to maintain skin moisture by increasing the production of a compound called hyaluronic acid. Hyaluronic acid supports skin hydration, and the increase in moisture improves "skin appearance, texture, and function."2

How Glycolic Acid Decreases the Signs of Aging

Glycolic Acid Treatments for Acne

Glycolic acid is available as (1) over-the-counter products and (2) professionally-administered chemical peels.

Over-the-counter products

Over-the-counter glycolic acid products all contain concentrations up to 10%. These products work by exfoliating the top layer of skin, reducing sebum, and decreasing skin hyperpigmentation. Due to the lower concentration, these products are safe to use at home, and while they can clear acne to some degree on their own, they are normally used alongside established acne medications.

Professionally-administered peels

Glycolic acid can also be applied in the form of a chemical peel. Chemical peels are not over-the-counter and must always be administered by a professional, such as an esthetician/cosmetician, nurse, or doctor. Chemical peels should never be attempted at home. A glycolic acid chemical peel most often contains glycolic acid at a concentration of 20 - 70%. A glycolic acid chemical peel, regardless of strength, works by:

  • Exfoliating the skin: Like all glycolic acid products, glycolic acid chemical peels thin the layer of dead skin cells that can accumulate on the surface of the skin. Exfoliating this dead skin cell layer helps to unclog pores.
  • Removing the keratin plug: Glycolic acid can break down the "sticky" protein keratin. Keratin works like glue and can stick skin cells together and promote skin cell accumulation on the surface of the skin. High-percentage chemical peels can help remove keratin plugs, which are structures formed from keratin and skin cells that clog the opening of the pore. The formation of a keratin plug can lead to acne, so removing keratin plugs can help prevent acne in the first place.
  • Removing the contents of an acne lesion: Removing a keratin plug enables the extrusion of the contents in clogged pores, which helps to clear them from the skin

Professionally-administered glycolic acid peels are effective at improving acne in people with mild to moderate acne, but less effective at clearing acne in people with severe forms of acne, including patients who present with several acne nodules and/or acne cysts.3

Characteristics that Affect the Strength of a Glycolic Acid Product

When using glycolic acid to treat acne, there are two factors that can alter its strength: (1) concentration, and (2) pH.

Concentration

  • Lower concentration (over-the-counter products)

    Generally, glycolic acid at concentrations up to 10% is safe for more frequent use and light exfoliation of the skin. These concentrations are found in topical medications or other over-the-counter glycolic acid products available for daily or recurrent use.
  • Higher concentration (professionally-administered peels)

    Professionally-administered glycolic acid products range in concentration of 20 - 70%. Glycolic acid products at these high concentrations are available in the form of deep chemical peels, and should never be applied at home.2,7

pH

pH is a scientific unit that measures the acidity of a compound. The pH scale ranges from 1 - 14, with "1" representing the most acidic substance and "14" representing the least acidic substance. For example, stomach acid has a pH of 2; water has a neutral pH of 7, and bleach has a pH of 12. The pH of the glycolic acid product can impact what effects it has on the skin and on acne. The lower the pH, the more effective glycolic acid is at clearing acne. However, a low pH also causes more side effects.

  • Higher pH: (over-the-counter products)

    The Food and Drug Administration (FDA) has determined the glycolic acid used for over-the-counter treatment of acne or other skin diseases must have a pH of 3.5 or greater
  • Lower pH (professionally-administered peels)

    Professionally-administered glycolic acid chemical peels can have a pH of 2 or lower. However, this low pH can lead to more severe side effects, and due to these side effects, only professionals should perform them.2,7

Glycolic Acid Side Effects

The side effects of glycolic acid products are generally mild, but professionally-administered glycolic acid chemical peels can have more severe side effects.

Over-the-counter products

Over-the-counter glycolic acid products may cause some mild side effects, including:

  • Mild skin irritation
  • Stinging
  • Burning
  • Mild pain
  • Itching

Important! Sun sensitivity: Increased sun sensitivity means that the skin is more prone to sunburn. Therefore, the FDA recommends that those using glycolic acid always wear some form of sun protection for the entire duration of treatment and for at least one week post-treatment.2,8

Side Effects of Over-the-counter Glycolic Acid Products

Professionally-administered peels

Glycolic acid at high concentrations and a low pH can cause much more serious side effects, including:

  • Pain
  • Skin blistering
  • Development of purple spots called purpura
  • Skin crusting
  • Redness
  • Skin discoloration
  • Skin cell death
  • Ulceration
  • Scarring

Due to the more severe side effects, only professionals should administer glycolic acid peels. If they were to be done at home and something went amiss, the person could hurt himself.8

Side Effects of Glycolic Acids

According to the FDA: Glycolic Acid Does Not Cause Cancer

Since glycolic acid can make the skin more prone to sunburn, several studies have investigated whether it can make the skin more prone to developing cancer.

Photodermatology, Photoimmunology and Photomedicine

A 2003 study published in Photodermatology, Photoimmunology and Photomedicine tested the ability of glycolic acid to cause cancer in mice. This study concluded that glycolic acid did not cause cancer in mice.

Further, the FDA has evaluated the cancer-causing ability of all AHAs, including glycolic acid, and determined, "[A]HA ingredients are not mutagenic or carcinogenic, are not reproductive or developmental toxins, and are not skin sensitizers." In other words, AHAs, including glycolic acid, do not cause cancer and do not affect pregnancy.2

Efficacy of Glycolic Acid on Acne

There are several studies investigating the effectiveness of both over-the-counter products and professionally-administered peels on acne.

Expand to read details of study on over-the-counter glycolic acid products

International Journal of Cosmetic Science

A 2015 study published in the International Journal of Cosmetic Science investigated the effectiveness of a 4% glycolic acid solution at clearing acne in 23 female acne patients. This study was performed through daily use of the 4% glycolic acid solution over the course of four weeks. The researchers found that the 4% glycolic acid treatment reduced non-inflammatory acne (whiteheads and blackheads) by 7.6% over four weeks. It is important to note that this study looked at glycolic acid as a sole treatment. In real life, glycolic acid is often combined with acne medications to achieve a better result.9

Expand to read details of studies on professionally-administered glycolic acid peels

Journal of the European Academy of Dermatology and Venereology

A 1999 study published in the Journal of the European Academy of Dermatology and Venereology investigated the efficacy of a 70% glycolic acid peel at clearing acne in 80 female acne patients. This study found that a 70% glycolic acid peel rapidly improved mild to moderate acne, and that it took an average of 6 peels to clear up moderate to severe acne. For severe acne with multiple acne nodules and cysts, the patients needed 8 - 10 peels before they observed an improvement in acne (moderate improvement in 5% of patients and marked improvement in 95% of patients) and acne scarring.10

Dermatologic Surgery

A 2008 study published in Dermatologic Surgery investigated the effectiveness of a 30% glycolic acid peel at clearing acne in 20 acne patients. This study used six peels performed at two-week intervals over 12 weeks. The researchers concluded that the 30% glycolic acid peel reduced the inflammatory acne lesion (papule and pustule) count by 43%.1

Journal of Cosmetic Laser Therapy

A 2010 study published in the Journal of Cosmetic Laser Therapy investigated the effectiveness of several different glycolic acid peel concentrations at clearing acne in 24 male and female acne patients. This study used 12 peels performed at two-week intervals over six months. The researchers found that the average number of acne lesions decreased from 47 to 17, which is a 63% reduction. The number of inflammatory acne lesions reduced by 29.1%, and the number of non-inflammatory acne lesions reduced by 62.7%.11

Journal of the European Academy of Dermatology and Venereology

A 2011 study published in the Journal of the European Academy of Dermatology and Venereology compared several studies investigating the effectiveness of glycolic acid peels at treating acne. This comparison led the researchers to draw four conclusions regarding the efficacy of glycolic acid peels.

1. The researchers found that the higher the concentration of glycolic acid, the more effective the peel was at clearing acne

2. The researchers concluded that as the number of peels performed on a patient increased, so did the efficacy, meaning that more peels provided better results

3. The researchers concluded that glycolic acid peels are most effective at treating mild acne, but can also help clear more severe acne. Acne was moderately improved in both groups, more than 0.5 improvement on a 0 - 5 acne grade in 50% of patients.

4. The researchers found that in some patients there was a flare of acne immediately following the beginning of treatment, meaning that the acne could get worse before it gets better3

Glycolic acid is somewhat effective at clearing acne, but needs to be used alongside acne medications, such as benzoyl peroxide, to achieve dramatic clearing of acne.

From this data, we can conclude that over-the-counter glycolic acid is somewhat effective at clearing acne, but needs to be used alongside acne medications, such as benzoyl peroxide, to achieve dramatic clearing of acne. On the other hand, professionally-administered glycolic acid peels may produce more significant results than over-the-counter glycolic acid. However, to achieve complete clearing of the skin, either type of glycolic acid should be combined with other treatments.

References:

  1. Kessler, E., Flanagan, K., Chia, C., Rogers, C. & Glaser, D. A. Comparison of α- and β-hydroxy acid chemical peels in the treatment of mild to moderately severe facial acne vulgaris. Dermatol Surg 34, 45 - 51 (2008). https://www.ncbi.nlm.nih.gov/pubmed/18053051
  2. Kornhauser, A., Coelho, S. G. & Hearing, V. J. Applications of hydroxy acids: classification, mechanisms, and photoactivity. Clin Cosmet Investig Dermatol 3, 135 - 142 (2010). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3047947/
  3. Dréno, B. et al. Efficacy of superficial chemical peels in active acne management - What can we learn from the literature today? Evidence-based recommendations. J Eur Acad Dermatol Venereol 25, 695 - 704 (2011). https://www.ncbi.nlm.nih.gov/pubmed/21029205
  4. Abdel Hay, R. et al. Cochrane Database of Systematic Reviews. 4, 1 - 45 (2016). https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD011946.pub2/references
  5. Garg, V. K., Sinha, S. & Sarkar, R. Glycolic acid peels versus salicylic-mandelic acid peels in active acne vulgaris and post-acne scarring and hyperpigmentation: a comparative study. Dermatol Surg 35, 59 - 65 (2009). https://www.ncbi.nlm.nih.gov/pubmed/19076192
  6. Erbagci, Z. & Akcali, C. Biweekly serial glycolic acid peels vs. long-term daily use of topical low-strength glycolic acid in the treatment of atrophic acne scars. Int J Dermatol 39, 789 - 794 (2000). https://www.ncbi.nlm.nih.gov/pubmed/11095203
  7. FDA. Alpha-Hydroxy Acids. https://www.fda.gov/cosmetics/productsingredients/ingredients/ucm107940.htm#q6
  8. Babilas, P., Knie, U. & Abels, C. Cosmetic and dermatologic use of alpha hydroxy acids. J Ger Soc Dermatol 10, 488 - 491 (2012). https://www.ncbi.nlm.nih.gov/pubmed/22916351
  9. Kim, S. J. et al. The effect of physically applied alpha hydroxyl acids on the skin pore and comedone. Int J Cosmet Sci 37, 519 - 525 (2015). https://www.ncbi.nlm.nih.gov/pubmed/26032934
  10. Atzori, L., Brundu, M. A., Orru, A. & Biggio, P. Glycolic acid peeling in the treatment of acne. J Eur Acad Dermatol Venereol 12, 119 - 122 (1999). https://www.ncbi.nlm.nih.gov/pubmed/10343939
  11. Ilknur, T., Demirtaşoğlu, M., Biçak, M. U. & Ozkan, S. Glycolic acid peels versus amino fruit acid peels for acne. J Cosmet Laser Ther 12, 242 - 5 (2010). https://www.ncbi.nlm.nih.gov/pubmed/20825257

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