Glycolic Acid Side Effects and Safety

Glycolic acid has a strong safety record spanning over 50 years of clinical use. At appropriate concentrations and pH levels, it is well-tolerated by most skin types and is approved for consumer use by both US and EU regulatory bodies [1] [2]. However, like any biologically active ingredient, it carries real risks when misused - and some side effects are expected even when used correctly. Understanding what is normal, what is concerning, and what to avoid entirely is essential for using glycolic acid safely.

Common Side Effects: What to Expect

When you first introduce glycolic acid into your routine, some degree of side effects is normal and expected. These alpha hydroxy acid side effects are signs that the acid is working - not signs that something is wrong. The key is knowing the difference between normal adjustment and a genuine adverse reaction.

Redness (Erythema)

Mild redness immediately after application is the most common side effect, particularly with leave-on products and peels. This occurs because glycolic acid increases blood flow to the treated area as part of the skin's natural response to a low-pH substance. The redness should be temporary - fading within 30 minutes to a few hours for daily-use products.

In clinical studies, erythema has been consistently reported as the most frequent side effect. Abels et al. (2011) found that even in an RCT comparing 10% glycolic acid to placebo, the glycolic acid group showed no statistically significant difference in tolerability from the placebo group [3]. This suggests that at well-formulated consumer concentrations, redness is typically mild.

Stinging and Tingling

A mild stinging or tingling sensation during and shortly after application is normal. This is caused by glycolic acid's activation of TRPV1 - a pH-sensitive ion channel on keratinocytes [4]. The sensation typically diminishes over the first 2–4 weeks as the skin acclimates.

Dryness and Flaking

Some dryness and light flaking, especially around the nose, chin, and forehead, is expected during the first 1–3 weeks of use. Glycolic acid accelerates the shedding of dead skin cells (corneodesmolysis), and until the skin adjusts its own hydration and turnover rate, the surface may feel drier than usual [5].

This is distinct from the deep dryness and tightness of over-exfoliation (discussed below). Normal adjustment-phase dryness responds well to a basic moisturizer and resolves on its own.

Mild Peeling

At higher concentrations or with professional peels, visible peeling is both expected and intentional. The controlled removal of surface cells is the entire purpose of a chemical peel. Light peeling typically begins 2–3 days after a professional treatment and resolves within 5–7 days. Do not pick or pull at peeling skin - let it shed naturally to avoid scarring or hyperpigmentation [6].

Photosensitivity: The Most Important Safety Consideration

The single most significant safety concern with glycolic acid is increased sensitivity to ultraviolet radiation. This is not a theoretical risk - it has been demonstrated in multiple controlled studies and is recognized by the US Food and Drug Administration [7].

What the Research Shows

Kaidbey et al. (2003) conducted a randomized, double-blind study in which 29 subjects applied 10% glycolic acid (pH 3.5) daily for four weeks. The results were clear: UV sensitivity increased by approximately 18%, measured as a decrease in the minimum erythemal dose (MED) - the amount of UV exposure required to produce visible redness. The study also found increased sunburn cell formation in treated skin [8].

Kornhauser et al. (2009), in an NIH-funded study, confirmed and expanded these findings. They demonstrated that 10% glycolic acid increased not only erythema but also UV-induced DNA damage and sunburn cell formation in human skin [9].

Important Context: The Risk Is Reversible

The increased photosensitivity is not permanent. Both the Kaidbey study and FDA review confirm that UV sensitivity returns to baseline within approximately one week of discontinuing glycolic acid use [7] [8].

Additionally, a large-scale National Toxicology Program study found that glycolic acid (at 4% and 10%, pH 3.5) did not increase photocarcinogenesis in an animal model. Despite enhancing acute UV sensitivity, glycolic acid does not appear to increase long-term cancer risk [10]. This does not eliminate the need for sunscreen - it means the risk is manageable with proper sun protection, not that it can be ignored.

Purging vs. Breakouts: How to Tell the Difference

One of the most confusing early experiences with glycolic acid is the "purge" - an initial worsening of breakouts that occurs in some users during the first 2–6 weeks of use. Understanding purging is critical because it can easily be mistaken for a bad reaction.

What Is Purging?

Purging occurs because glycolic acid accelerates cell turnover. Microcomedones - tiny, pre-existing clogged pores that have not yet surfaced - are pushed to the surface faster than they would naturally appear. The result is a temporary increase in whiteheads, small pimples, or closed comedones in areas where you typically break out [5].

How to Tell Purging From a True Breakout

| Feature | Purging | Adverse Reaction | |---------|---------|-----------------| | Location | Areas where you typically break out | New areas where you don't usually get acne | | Type of lesion | Small whiteheads, closed comedones | Deep cysts, widespread inflammation, hives | | Timeline | Resolves within 2–6 weeks | Persists or worsens beyond 6–8 weeks | | Progression | Improves gradually | Gets worse over time | | Other symptoms | No unusual pain, swelling, or itching | May include burning, swelling, or rash |

When to Stop

If any of the following occur, discontinue use and consult a dermatologist:

• Breakouts appear in entirely new areas
• Deep, painful cystic lesions develop
• Widespread rash or hives
• Breakouts continue to worsen after 6–8 weeks with no improvement
• Any signs of allergic reaction (swelling, difficulty breathing)

Over-Exfoliation: Signs, Causes, and Recovery

Over-exfoliation is the most common form of glycolic acid misuse. It happens when the skin's barrier is damaged faster than it can repair itself - typically from using too high a concentration, too frequently, or in combination with other exfoliating actives.

Signs of Over-Exfoliation

• Persistent redness that does not fade between applications
• Increased sensitivity - products that previously felt fine now sting or burn
• Tight, "raw" feeling even after moisturizing
• Unusual dryness or flaking that does not improve with hydration
• Shiny, almost "glassy" appearance to the skin surface - indicating the dead cell layer has been stripped too thin
• Increased breakouts - a compromised barrier is more susceptible to bacterial infection and inflammation [11]

Common Causes

• Using glycolic acid daily before the skin has adjusted
• Combining glycolic acid with retinoids, other AHAs/BHAs, or high-concentration vitamin C without spacing them appropriately
• Using a high-concentration product (>10%) without building tolerance first
• Applying glycolic acid to skin that is already compromised (sunburned, windburned, freshly waxed)

How to Recover

If you suspect over-exfoliation:

1. Stop all exfoliating actives immediately. This includes glycolic acid, salicylic acid, retinoids, vitamin C serums, and physical scrubs.
2. Simplify your routine to a gentle cleanser, a ceramide- or niacinamide-based moisturizer, and sunscreen. Nothing else.
3. Give your skin 2–4 weeks to rebuild its barrier. The stratum corneum takes approximately 2–4 weeks to regenerate its full protective capacity.
4. Reintroduce glycolic acid slowly - start at a lower concentration, lower frequency, and consider buffering with moisturizer.

Contraindications: When to Avoid Glycolic Acid

Certain conditions and situations make glycolic acid use inappropriate or require special medical supervision.

Active Inflammatory Skin Conditions

Glycolic acid should not be used on skin with active eczema, rosacea, psoriasis, or contact dermatitis. These conditions involve a compromised epidermal barrier and active inflammation. Applying an acid to already-inflamed skin will worsen irritation and may trigger a flare [11].

Once the condition is in remission and the barrier has healed, glycolic acid may be reintroduced under dermatological guidance - but this requires professional assessment, not self-treatment.

Open Wounds, Sunburn, and Broken Skin

Never apply glycolic acid to cuts, scrapes, open acne lesions, or sunburned skin. The acid will penetrate damaged tissue far more deeply than intact skin, causing pain and potential scarring.

Recent Isotretinoin (Accutane) Use

Isotretinoin significantly thins the stratum corneum and alters the skin's barrier function. Most dermatologists recommend waiting at least 6 months after completing an isotretinoin course before introducing any chemical exfoliant, including glycolic acid [6].

Recent Procedures

After laser treatments, microdermabrasion, microneedling, or other resurfacing procedures, the skin needs time to heal before any acid is applied. Follow your practitioner's specific guidance on when to resume chemical exfoliation - this typically ranges from 1–4 weeks depending on the procedure.

Pregnancy and Breastfeeding Considerations

This is an area where the evidence is nuanced and honest communication matters.

No controlled human pregnancy studies have been conducted on glycolic acid. The safety assessment is based on three factors:

1. Minimal systemic absorption. Topical glycolic acid at consumer concentrations is absorbed primarily into the epidermis and upper dermis. The amount reaching the bloodstream is negligible [12].
2. Animal data. Adverse reproductive effects in animal studies occurred only at doses far exceeding what topical cosmetic use delivers [12].
3. Professional consensus. The American College of Obstetricians and Gynecologists (ACOG) considers glycolic acid safe during pregnancy. Trivedi et al. (2017) reviewed cosmetic procedures during pregnancy and concluded that glycolic acid and lactic acid peels are considered safe at concentrations below 10% [13].

Skin of Color Considerations

Glycolic acid is used across all Fitzpatrick skin types, but people with darker skin tones (Fitzpatrick IV–VI) face a specific additional risk: post-inflammatory hyperpigmentation (PIH).

The PIH Risk

PIH occurs when inflammation or injury triggers melanocytes to overproduce melanin, leaving dark spots at the site of irritation. Because melanocytes in darker skin are inherently more reactive, even mild irritation from glycolic acid - redness, stinging, or micro-inflammation - can trigger PIH [14].

This risk increases with:

• Higher glycolic acid concentrations
• Lower pH (more aggressive formulations)
• Longer contact times
• Application to already-irritated skin

Evidence in Darker Skin Types

Burns et al. (1997) studied glycolic acid peels (up to 68%) in Fitzpatrick IV–VI patients and found that the peels were effective for treating existing PIH with minimal adverse effects when properly administered [14]. Sarkar et al. (2012) reviewed chemical peel use in dark-skinned patients and concluded that glycolic acid is among the safer options for this population, provided lower concentrations, shorter contact times, and gradual escalation are used 15.

Drug Interactions and Ingredient Conflicts

Glycolic acid does not have systemic drug interactions in the traditional pharmacological sense, because topical application results in negligible systemic absorption. However, it has significant topical interactions - combinations with other skincare actives that increase the risk of irritation or reduce efficacy.

High-Risk Combinations

• Glycolic acid + retinoids (retinol, tretinoin, adapalene): Both exfoliate the skin through different mechanisms. Used simultaneously (same application), they significantly increase irritation risk. However, they can be used in the same routine if separated by time (e.g., glycolic acid in the evening, retinoid on alternate nights) and tolerance has been established. See our retinol comparison for a detailed breakdown.
• Glycolic acid + other AHAs or BHA (salicylic acid): Layering multiple exfoliating acids in a single application amplifies the total acid exposure. Use one per session unless the product is specifically formulated to contain both.
• Glycolic acid + high-concentration vitamin C (L-ascorbic acid at 15%+): Both require low pH and can cause cumulative irritation. Some users tolerate both, but introduce them separately and monitor carefully.
• Glycolic acid + benzoyl peroxide: Benzoyl peroxide can oxidize glycolic acid, potentially reducing its efficacy. Apply at different times of day if using both.

Use our interaction checker to verify specific ingredient combinations before layering products.

Low-Risk Companions

• Hyaluronic acid: A humectant, not an active. Safe and beneficial to layer with glycolic acid to counteract dryness.
• Niacinamide (vitamin B3): Despite an old internet myth, niacinamide and glycolic acid can be used together safely. Niacinamide's anti-inflammatory properties may actually help mitigate glycolic acid irritation.
• Ceramides: Barrier-repairing lipids that complement glycolic acid use, especially during the adjustment period.
• Peptides: Generally stable and well-tolerated alongside glycolic acid.

When to See a Dermatologist

Most glycolic acid side effects are manageable at home with dose adjustment and patience. However, certain situations require professional evaluation:

• Severe burning, blistering, or crusting after application - this may indicate a chemical burn from a product that is too strong or was left on too long
• Signs of allergic contact dermatitis - widespread rash, swelling, or hives that extend beyond the application area
• Persistent worsening breakouts beyond 8 weeks of use - this is not purging and suggests the product is not appropriate for your skin
• New or worsening hyperpigmentation - especially in darker skin tones, where PIH from glycolic acid use would require a modified approach
• Any side effect that causes significant discomfort or anxiety - a dermatologist can help determine whether the reaction is normal or concerning, and suggest alternative approaches if needed

The Safety Bottom Line

Glycolic acid is one of the most extensively studied and well-characterized ingredients in dermatology. The National Toxicology Program has evaluated its long-term safety [10]. The CIR Expert Panel has established clear concentration and pH guidelines for consumer use (10% maximum at pH 3.5 or above) 1 - our free acid calculator shows exactly how much active acid that limit allows. The FDA requires appropriate labeling for UV sensitivity [7].

The risks are real but manageable:

• Photosensitivity is addressed with daily sunscreen
• Normal adjustment effects (mild redness, stinging, dryness) resolve within 2–4 weeks
• Over-exfoliation is prevented by starting low and going slow
• Purging is temporary and resolves within 2–6 weeks
• Contraindications are clearly defined and avoidable

The most important safety practice is not choosing a specific product - it is building your routine gradually, protecting your skin from UV exposure, and paying attention to how your skin responds. For a step-by-step guide to introducing glycolic acid safely, see our how to use glycolic acid guide. To understand the science behind its mechanisms, see our guide on how glycolic acid works.

References

1. Andersen FA. "Final Report on the Safety Assessment of Glycolic Acid, Ammonium, Calcium, Potassium, and Sodium Glycolates..." Int J Toxicol. 1998;17(Suppl 1):1-241. doi:10.1177/109158189801700101
2. Scientific Committee on Consumer Safety (SCCS). Opinion on Alpha-Hydroxy Acids. SCCNFP/0370/00. 2000.
3. Abels C, Kaszuba A, Michalak I, et al. "A 10% glycolic acid containing oil-in-water emulsion improves mild acne: a randomized double-blind placebo-controlled trial." J Cosmet Dermatol. 2011;10(3):202-209. doi:10.1111/j.1473-2165.2011.00572.x
4. Kim SJ, Won YH. "Glycolic acid induces keratinocyte proliferation in a skin equivalent model via TRPV1 activation." J Dermatol Sci. 2010;57(3):197-199. doi:10.1016/j.jdermsci.2009.12.004
5. Sharad J. "Glycolic acid peel therapy - a current review." Clin Cosmet Investig Dermatol. 2013;6:281-288. doi:10.2147/CCID.S34029
6. American Academy of Dermatology. "Chemical Peels." Patient education resource. aad.org
7. US Food and Drug Administration. "Alpha Hydroxy Acids - Cosmetic Ingredients." fda.gov. Guidance for Industry: Labeling for Cosmetics Containing Alpha Hydroxy Acids. January 2005.
8. Kaidbey K, Sutherland B, Bennett P, et al. "Topical glycolic acid enhances photodamage by ultraviolet light." Photodermatol Photoimmunol Photomed. 2003;19(1):21-27. doi:10.1034/j.1600-0781.2003.00013.x
9. Kornhauser A, Wei RR, Yamaguchi Y, et al. "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 Sci. 2009;55(1):10-15.
10. National Toxicology Program. "Photocarcinogenesis study of glycolic acid and salicylic acid in SKH-1 mice." NTP Tech Rep. 2007;524:1-242.
11. Tang SC, Yang JH. "Dual Effects of Alpha-Hydroxy Acids on the Skin." Molecules. 2018;23(4):863. doi:10.3390/molecules23040863
12. Bozzo P, Chua-Gocheco A, Einarson A. "Safety of skin care products during pregnancy." Can Fam Physician. 2011;57(6):665-667.
13. Trivedi MK, Kroumpouzos G, Murase JE. "A review of the safety of cosmetic procedures during pregnancy and lactation." Int J Womens Dermatol. 2017;3(1):6-10.
14. Burns RL, Prevost-Blank PL, Lawry MA, et al. "Glycolic acid peels for postinflammatory hyperpigmentation in black patients. A comparative study." Dermatol Surg. 1997;23(3):171-174.
15. Sarkar R, Garg S, Bansal S, Sethi S. "Chemical peels for melasma in dark-skinned patients." J Cutan Aesthet Surg. 2012;5(4):247-253.

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This article is for informational purposes only and does not constitute medical advice. Consult a board-certified dermatologist before starting any new skincare treatment.