Which active ingredients can glycolic acid be combined with?

The niacinamide is a versatile active ingredient that soothes redness, reduces pigmentation spots by limiting melanin transfer to keratinocytes, and strengthens the skin barrier by stimulating ceramide synthesis. When combined with glycolic acid, it counterbalances the sensitivity sometimes induced by this AHA while enhancing its efficacy.

A prospective two-month study of 25 women with mild acne confirmed the benefit of this synergy. After eight weeks of daily application of a gel containing these two active ingredients, results showed an approximately 80% reduction in acne lesions, corroborated by a significant improvement in the clinical GAGS (Global Acne Grading System) score used to assess acne severity. A decrease in inflammation and pigmentary disturbances was also observed, while skin barrier function remained intact, demonstrating good tolerability.

Although this combination works in the same formulation, it is not recommended to layer two distinct products. Glycolic acid requires an acidic pH (3–4) to be effective, and applying a niacinamide serum (pH 5–7) can reduce its exfoliating action.

The combination of glycolic acid with retinoids is based on the complementary nature of their mechanisms of action. Retinoids (retinol, retinal, retinoic acid, etc.) are renowned for their ability to normalize cell turnover, reduce inflammation, and stimulate collagen synthesis, thereby helping to diminish skin imperfections and acne scars. Combined with the keratolytic properties of glycolic acid, they offer a particularly beneficial synergy for acne-prone skin or skin with irregular pigmentation.

A twelve-week clinical study involving 35 patients aged 17 to 34 years evaluated the efficacy of a combination of glycolic acid (12%) and retinoic acid (0.025%). The results revealed a significant improvement in scarring in 91.4% of participants, confirming the efficacy of this combination and its potential as an alternative to more invasive treatments.

Although combining glycolic acid with retinoids is effective, we do not recommend this combination for sensitive skin.

The vitamin C (ascorbic acid) is recognized for its antioxidant and brightening properties: it neutralizes free radicals responsible for oxidative stress and inhibits tyrosinase activity, thereby limiting melanin synthesis. When combined with glycolic acid—whose exfoliating action enhances active ingredient penetration—the efficacy of vitamin C is potentiated, particularly for reducing hyperpigmentation.

A clinical study conducted on 178 melasma patients (MASI score > 10) compared two protocols: a 40% glycolic acid peel every two weeks with daily application of a vitamin C cream, versus a standard treatment of hydroquinone (4%), tretinoin, and corticosteroids. After six weeks, 94.4% of patients in the glycolic acid + vitamin C group showed a significant improvement in hyperpigmentation, compared to 79.8% in the control group, confirming the potential of this combination as an effective and better-tolerated alternative to conventional depigmenting treatments.

The combination of glycolic acid and pure vitamin C can be too irritating for sensitive skin.

Thehyaluronic acid is renowned for its hydrating properties, able to retain up to 1,000 times its weight in water depending on its molecular weight. As a flagship active ingredient in cosmetics, it helps restore the skin’s barrier function and limit water loss, providing comfort and suppleness. When combined with glycolic acid, it mitigates potential sensations of tightness and reduces the risk of intolerance without compromising the latter’s exfoliating effect.

A clinical study conducted on 100 patients with melasma compared several depigmenting regimens: hydroquinone alone (group 1), hydroquinone + glycolic acid (group 2), hydroquinone + hyaluronic acid (group 3), hydroquinone + glycolic acid + hyaluronic acid (group 4), and placebo (group 5). After 12 weeks, all hydroquinone-containing groups demonstrated an improvement in MASI score reflecting reduced hyperpigmentation, while the addition of hyaluronic acid reduced the frequency and severity of glycolic acid–related adverse effects, enhancing its tolerability.

The combination of glycolic acid with salicylic acid is based on the principle of merging two complementary exfoliants. Thesalicylic acid (BHA), sebum-soluble, penetrates pores to unclog comedones, while glycolic acid works at the surface to exfoliate the epidermis. This pairing enables a more thorough cleansing and optimizes the reduction of imperfections.

A study involving 66 patients with mild to moderate inflammatory acne evaluated a serum containing these two acids, applied each evening for two weeks. Over 90% of participants observed a significant improvement in acne, with reductions in comedones and cystic lesions, and 70 to 80% reported less oily, more even skin.

Although highly effective againstblemishes, this combination is not recommended for sensitive skin.

Theazelaic acid is a dicarboxylic acid with anti-inflammatory, antibacterial, and depigmenting properties. It reduces the proliferation of Cutibacterium acnes, soothes the skin, and targets hyperpigmentation by inhibiting tyrosinase. When combined with glycolic acid, it supports a smoother, more even complexion.

A study involving 70 patients with acne compared a 20% azelaic acid cream plus a 15% glycolic acid lotion to a 0.025% tretinoin solution, applied twice daily for 12 weeks. The azelaic acid/glycolic acid combination significantly reduced acne lesions, with efficacy comparable to tretinoin for noninflammatory lesions and superior efficacy for inflammatory lesions, while offering better tolerability (less dryness, redness, and peeling).

The bakuchiol is a plant-derived active ingredient often touted as a gentle alternative to retinol. It promotes cell turnover, stimulates collagen synthesis, and exhibits antioxidant and anti-inflammatory properties. It thus contributes to improving the appearance of fine lines, uneven skin texture, and pigmentation spots.

When combined with glycolic acid, bakuchiol may potentiate the effects of exfoliation and cellular renewal without increasing the irritation risks often associated with this AHA. This combination therefore appears promising for smoothing the skin and evening out skin tone.

Even though combining glycolic acid and bakuchiol appears intriguing from a theoretical standpoint, no clinical study has yet assessed the efficacy or tolerability of this combination.

Thealpha-arbutin is a natural derivative of hydroquinone recognized for its gentle and better-tolerated brightening action. It works by inhibiting tyrosinase activity, thereby limiting melanin production responsible for brown spots. Unlike hydroquinone, it is considered safer for cosmetic use, making it a popular ingredient in skincare formulations aimed at evening out skin tone. Combining arbutin with glycolic acid could theoretically enhance their respective efficacies: by exfoliating the epidermis’s superficial layers, glycolic acid would facilitate alpha-arbutin penetration, optimizing its depigmenting action.

However, to date, no scientific study has evaluated the combination of glycolic acid and arbutin. The potential benefits therefore remain hypothetical.

Combining glycolic acid with lactic acid or mandelic acid may seem redundant, since all three belong to the alpha-hydroxy acid (AHA) family. However, they act in complementary ways to refine skin texture while minimizing the risk of irritation, thereby creating beneficial synergies.

When combined withlactic acid, glycolic acid benefits from its gentler action and its humectant properties, which support hydration while strengthening cell cohesion. This synergy was investigated in a clinical study assessing the efficacy of a peel containing 2% glycolic acid and 2% lactic acid, applied to the faces of 23 women with acne-prone skin. The results showed a significant reduction in both open and closed comedones as early as the first week, with only transient irritation reported in two participants.

L-mandelic acid also represents a relevant combination. Its large molecular size limits its skin penetration, providing a gradual and better-tolerated effect, particularly suited to sensitive skin. A pilot study using a multi-acid gel (including 16% glycolic acid, 8% lactic acid, and 5% mandelic acid, among others) demonstrated acne improvement as early as the third week and scar reduction after four weeks, without significant side effects. Although it remains difficult to draw precise conclusions about the specific synergy between glycolic acid and mandelic acid due to the presence of other exfoliants, the study confirms their compatibility.

Ultimately, combining glycolic acid with other AHAs allows for the modulation of exfoliation intensity according to skin-specific needs : the rapid, deep action of glycolic acid is counterbalanced by the milder, hydrating, and progressive effects of lactic and mandelic acids. These combinations offer a nuanced approach to chemical exfoliation, adaptable to various skin types and tolerance levels.

The glycerin is one of the most commonly used humectants in cosmetics, recognized for its ability to attract and retain water in the stratum corneum. It reinforces the skin’s barrier function, reduces dehydration, and enhances elasticity. Glycerin also provides an occlusive effect by forming a thin film on the epidermal surface that minimizes water loss. In formulations, glycerin often acts as a protective agent and is frequently employed to counterbalance the irritating effects of certain active ingredients, such as glycolic acid, thereby ensuring better tolerance.

The incorporation of glycerin with glycolic acid is widespread in cosmetic formulations because it helps minimize the side effects associated with glycolic acid while preserving its exfoliating effectiveness.

Thekojic acid, of fungal origin, is recognized for its ability to reduce the appearance of brown spots and even out skin tone. When combined with glycolic acid, which exfoliates the stratum corneum and promotes cellular renewal, its efficacy is enhanced. A study of 40 women with melasma compared the application of a gel containing 10% glycolic acid and 2% hydroquinone, with or without 2% kojic acid, on each half of the face twice daily for 12 weeks. Improvement was observed on both sides, but the side treated with kojic acid showed superior results: 60% of patients saw more than half of their melasma disappear, compared to 47.5% on the other side, including two cases of complete clearance. Side effects (redness, tingling) were transient and resolved by the third week. The study concludes that adding kojic acid helps to boost the effectiveness of glycolic acid.

Caution is warranted with kojic acid, which is suspected of acting as an endocrine disruptor and of being allergenic, mutagenic, and carcinogenic.

The benzoyl peroxide is an essential compound in the management of acne due to its antibacterial properties, which are particularly effective against Cutibacterium acnes, the bacterium involved in the worsening of acne. It also has an exfoliating effect and helps reduce skin inflammation.

Combining benzoyl peroxide and glycolic acid could theoretically be relevant for reducing blemishes, whether they are comedones or inflammatory lesions (papules and pustules). However, no study has examined the association of glycolic acid and benzoyl peroxide, and the irritating potential of these two agents remains a significant limitation.

We advise against using glycolic acid products and benzoyl peroxide products together, as this could irritate your skin.

Hydroquinone is a reference depigmenting agent known for its ability to lighten dark spots by inhibiting the enzyme tyrosinase. However, its use is regulated due to potential side effects, including irritation, redness, or allergic reactions. Although theoretically, its penetration could be enhanced by combining it with glycolic acid, this appears not to provide any additional benefit: one study demonstrated that the combination did not further improve the MASI score compared to hydroquinone alone, while it increased the frequency of adverse effects.

Thus, even though the combination of glycolic acid and hydroquinone may seem appealing on paper, it is not necessarily relevant. In Europe, hydroquinone is permitted only for professional use.

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• NAVALE S. & al. Combination of retinoic acid and glycolic acid in the treatment of acne scars. Indian Dermatology Online Journal (2015).

• SHIN M. K. & al. The impact of topically applied alpha hydroxy acids on skin pores and comedones. International Journal of Cosmetic and Dermatology (2015).

• FARAG S. E. & al. Evaluation of the efficacy and safety of combinations of hydroquinone, glycolic acid, and hyaluronic acid in the treatment of melasma. Journal of Cosmetic Dermatology (2015).

• HADDAD L. & al. Two is better than one: The combined effects of glycolic acid and salicylic acid on acne-related disorders. Journal of Cosmetic Dermatology (2020).

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• ASLAM K. & al. Effectiveness of 40% glycolic acid peel and topical vitamin C cream compared to a triple combination cream in treating epidermal melasma. Khyber Journal of Medical Sciences (2023).