What Is Glycolic Acid? A Complete Guide

Glycolic acid is an alpha hydroxy acid (AHA) derived from sugarcane. It is the smallest molecule in the AHA family, which allows it to penetrate the skin more effectively than any other acid in its class. Dermatologists and skincare professionals use glycolic acid to accelerate cell turnover, improve skin texture, reduce fine lines, and treat hyperpigmentation. It is one of the most extensively studied ingredients in dermatology, with decades of clinical research supporting its use [1].

What Is Glycolic Acid?

Glycolic acid (chemical formula: C2H4O3) -- also known by its IUPAC name alpha hydroxy acetic acid or hydroxyacetic acid -- is the simplest alpha hydroxy acid. It occurs naturally in sugarcane, beets, and unripe grapes, though most cosmetic-grade glycolic acid is now synthesized for purity and consistency [2].

The term "alpha hydroxy acid" refers to a group of organic acids where a hydroxyl group is attached to the carbon atom adjacent to (alpha to) the carboxyl group. Other members of the AHA family include lactic acid (from milk), mandelic acid (from almonds), tartaric acid (from grapes), and citric acid (from citrus fruits). You can compare glycolic acid to other AHAs to understand what makes each one different. What sets glycolic acid apart is its size: at just 76.05 daltons, it is the smallest AHA, which directly determines how deeply and quickly it can penetrate the outermost layer of skin [3].

Where Does Glycolic Acid Come From?

Historically, glycolic acid was extracted from sugarcane juice - which is why early skincare formulations were sometimes marketed as "sugarcane extract." Today, most glycolic acid in skincare products is produced synthetically via the reaction of formaldehyde with carbon monoxide and water, or through the hydrolysis of chloroacetic acid. Synthetic production ensures consistent purity and pH, which are critical for both safety and efficacy.

How Glycolic Acid Works on Skin

Glycolic acid works through two well-documented mechanisms that operate at different depths of the skin.

Surface Exfoliation (Epidermis)

At the surface, glycolic acid disrupts the protein-based junctions - called desmosomes (or corneodesmosomes in the stratum corneum) - that hold dead corneocytes (skin cells) together.

The result is smoother, more even-toned skin and reduced buildup that can clog pores [2].

Dermal Stimulation (Dermis)

At higher concentrations and low pH, glycolic acid penetrates beyond the epidermis and stimulates fibroblasts in the dermis. Research by Bernstein et al. demonstrated that topical application of 20% glycolic acid lotion to forearm skin twice daily for three months increased type I collagen mRNA and hyaluronic acid content, which contributes to improved firmness and hydration over time [1]. A separate study by Ditre et al. found that AHA treatment reversed markers of photoaging in both the epidermis and dermis [4].

Benefits Overview

Glycolic acid has a broad range of evidence-backed benefits for skin. These include:

• Exfoliation and smoother texture - accelerated removal of dead skin cells reveals fresher, smoother skin underneath [2]
• Reduced fine lines and wrinkles - stimulation of collagen synthesis helps improve the appearance of aging skin [1]
• Faded hyperpigmentation - faster cell turnover helps disperse melanin deposits that cause dark spots and uneven tone [4]
• Acne prevention - by keeping pores clear of dead cell buildup, glycolic acid may help reduce comedonal acne [5]
• Improved hydration - glycolic acid increases hyaluronic acid in the skin, which draws and retains moisture [1]

For a detailed breakdown of each benefit with supporting research, see our complete guide to glycolic acid benefits.

Common Forms and Concentrations

Glycolic acid appears in a wide range of skincare product formats. The right choice depends on your experience level, skin sensitivity, and goals. Browse our curated list of glycolic acid products to see options across every category below.

Daily-Use Products (2%–10%)

• Cleansers (2%–5%): 5%(Low concentration) Brief skin contact time means gentle exfoliation. Good for beginners or as a daily maintenance step.
• Toners (5%–10%): Applied with a cotton pad and left on the skin. Moderate exfoliation with daily or every-other-day use.
• Serums (5%–10%): Concentrated formulas designed to be layered under moisturizer. Often combined with hydrating ingredients like hyaluronic acid.

Treatment Products (10%–20%)

• Leave-on treatments and masks (10%–15%): 15%(Medium concentration) Applied for a set period (5–20 minutes), then rinsed or left on depending on the product. More noticeable exfoliation; typically used 1–3 times per week.
• At-home peels (15%–20%): Short-contact treatments that produce visible peeling and renewal. Recommended for experienced users who have built tolerance over time.

Professional Treatments (20%–70%)

• Light peels (20%–35%): Performed by licensed aestheticians. Treat surface texture, mild acne scarring, and dullness.
• Medium-depth peels (50%–70%): 50%(High concentration) Performed by dermatologists. Address deeper wrinkles, significant sun damage, and moderate hyperpigmentation.

Who Should Use Glycolic Acid

Glycolic acid is suitable for most skin types and a wide range of concerns. It is particularly beneficial for people dealing with:

• Dull, rough, or uneven skin texture - the exfoliating action reveals smoother skin
• Fine lines and early signs of aging - collagen stimulation provides modest improvement over weeks to months
• Post-acne dark spots or sun spots - accelerated turnover helps fade hyperpigmentation
• Clogged pores and blackheads - surface-level exfoliation prevents dead cell buildup in pores
• Dry or dehydrated skin - glycolic acid's humectant properties and hyaluronic acid stimulation may improve moisture retention

Who Should Avoid Glycolic Acid

While glycolic acid is generally well-tolerated, certain individuals should use it with caution or avoid it entirely:

• Active eczema, rosacea, or dermatitis - glycolic acid can worsen inflammation in already-compromised skin barriers
• Open wounds, cuts, or sunburned skin - never apply acid to broken or actively inflamed skin
• Recent isotretinoin (Accutane) use - the skin barrier is significantly thinned during and after isotretinoin treatment; most dermatologists recommend waiting at least 6 months
• Concurrent use of multiple strong actives - combining glycolic acid with retinoids, other AHAs/BHAs, or high-concentration vitamin C without proper spacing can lead to over-exfoliation
• Pregnancy and breastfeeding - while low-concentration topical glycolic acid is considered low-risk by many dermatologists due to minimal systemic absorption, no controlled studies exist; discuss with your OB-GYN or dermatologist before use
• Very sensitive skin - if your skin reacts to most active ingredients, consider a gentler AHA like mandelic or lactic acid first (see our skin types guide for tailored recommendations)

For a comprehensive discussion of side effects and risk factors, see our side effects and safety guide.

How to Start Using Glycolic Acid

If you are new to glycolic acid, the most important rule is to start low and go slow:

1. Patch test first. Apply a small amount to your inner forearm or behind your ear. Wait 24–48 hours for any adverse reaction.
2. Begin with a low concentration (5%–7%). A toner or serum is a good starting format. See our concentration guide for help choosing the right strength.
3. Use it 2–3 times per week, ideally in your evening routine.
4. Apply sunscreen every morning. This is mandatory, not optional.
5. Increase frequency gradually once your skin adjusts - typically after 2–4 weeks.

For a step-by-step beginner-to-advanced guide, see how to use glycolic acid.

Is glycolic acid safe for daily use?

For most people, yes - at lower concentrations (2%–7%). However, daily use is not necessary for everyone. Many dermatologists recommend starting at 2–3 times per week and increasing only if your skin tolerates it well. Signs that you are over-exfoliating include persistent redness, stinging, or a tight, "raw" feeling [3].

Can I use glycolic acid if I have sensitive skin?

You can, but with caution. Start with the lowest available concentration (2%–5%), buffer it with moisturizer, and limit use to once or twice per week. If your skin reacts strongly even at low concentrations, a gentler AHA such as mandelic acid or polyhydroxy acid (PHA) may be a better fit. Always consult a dermatologist if you are unsure.

Is glycolic acid better than salicylic acid?

Neither is universally "better" - they serve different purposes. Glycolic acid is water-soluble and works primarily on the skin surface, making it ideal for texture, tone, and anti-aging. Salicylic acid is oil-soluble, which allows it to penetrate into pores, making it more effective for acne and oily skin. Many people benefit from both at different times. See our glycolic acid vs salicylic acid comparison for a detailed breakdown.

Does glycolic acid cause purging?

Yes, glycolic acid can trigger a temporary "purge" - an initial increase in breakouts during the first 2–6 weeks of use. This happens because the accelerated cell turnover pushes pre-existing microcomedones (clogged pores that haven't yet surfaced) to the surface faster. Purging typically resolves on its own. If new breakouts persist beyond 6–8 weeks, the product may not be right for your skin, and you should consult a dermatologist.

Can glycolic acid remove acne scars?

Glycolic acid can help improve the appearance of shallow, discolored acne marks (post-inflammatory hyperpigmentation). However, it has limited ability to address deep pitted or ice-pick scars, which involve structural damage to the dermis. For deeper scarring, dermatologists typically recommend procedures such as microneedling, fractional laser resurfacing, or TCA cross. Glycolic acid can be part of a broader treatment plan but should not be relied on as a standalone solution for significant scarring [4].

References

1. 1. 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
2. 2. Sharad J. (2013). Glycolic acid peel therapy - a current review. Clin Cosmet Investig Dermatolreview
3. 3. Tang SC, Yang JH. (2018). Dual Effects of Alpha-Hydroxy Acids on the Skin. Moleculesreview
4. 4. Ditre CM, Griffin TD, Murphy GF, et al. (1996). Effects of alpha-hydroxy acids on photoaged skin: a pilot clinical, histologic, and ultrastructural study. J Am Acad Dermatolclinical trial
5. 5. Dréno B, Bissonnette R, Gagné-Henley A, et al. (2021). Safety review of skin care products for acne-prone skin. Clin Cosmet Investig Dermatolreview
6. 6. Kornhauser A, Wei RR, Yamaguchi Y, et al. (2009). The effects of topically applied glycolic acid and salicylic acid on ultraviolet radiation-induced erythema, DNA damage and sunburn cell formation in human skin. J Dermatol Sciclinical trial
7. 7. Green BA, Yu RJ, Van Scott EJ. (2009). Clinical and cosmeceutical uses of hydroxyacids. Clin Dermatolreview
8. 8. American Academy of Dermatology. (2023). Chemical Peels. Patient education resourceguideline

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