Glycolic or Salicylic Acid: Which Form Should You Opt For?

Glycolic acid, derived from sugar cane, belongs to the family of alpha-hydroxy acids (AHAs). AHAs are characterised by their hydroxyl group (-OH) being attached to the carbon atom adjacent to the carboxylic acid group (-COOH), which is what defines them as ‘alpha.’ This structure makes glycolic acid highly water-soluble and effective in aqueous environments.

Its small molecular size enables it to readily permeate the skin's protective barrier, specifically targeting the uppermost layer, known as the stratum corneum. Here, glycolic acid breaks down the bonds between dead skin cells, aiding their removal and promoting a smoother, more radiant complexion. By exfoliating the surface layer, glycolic acid also enhances the absorption of other skin-care ingredients and can assist in stimulating collagen production over time. These combined properties render glycolic acid an effective solution for the following:

• Lacklustre Skin: By exfoliating dead epidermal cells, glycolic acid reveals fresher, more radiant skin beneath.

• Fine Lines and Wrinkles: Regular application may help diminish the appearance of fine lines and refine skin texture by stimulating collagen synthesis.

• Hyperpigmentation: It helps to even skin tone and reduce the appearance of dark spots through regular exfoliation.

Who Should Utilise Glycolic Acid?

Glycolic acid is suitable for all skin types, but is most effective for individuals with normal to dry skin, particularly those seeking to address signs of ageing or to enhance skin texture and tone. In everyday skincare products, it is most commonly found in concentrations ranging from 2% to 10%.

Salicylic acid, a beta-hydroxy acid (BHA), is characterised by its oil-soluble nature and its unique chemical structure. Unlike alpha-hydroxy acids, salicylic acid’s hydroxyl group is attached to the second carbon atom from the carboxyl group—hence the ‘beta’. This arrangement, together with its phenolic ring, renders salicylic acid lipophilic, enabling it to dissolve readily in the skin’s natural oils.

This oil solubility enables salicylic acid to penetrate deeply into blocked pores, breaking down excess sebum and dead skin cells. Derived from willow bark, it's most commonly recommended for:

• Acne and Breakouts: Its capacity to dissolve sebum makes it particularly effective at clearing blocked pores, which helps to reduce acne and prevent future breakouts.

• Oily Skin: Salicylic acid helps to regulate excess oil production, which benefits those with oily or combination skin types. Therefore, if you are experiencing overactive sebaceous glands and excessive sebum production, salicylic acid could well be the solution for you.

• Blackheads and Whiteheads: By exfoliating within the pores, salicylic acid helps remove impurities and prevent open comedones (blackheads) and closed comedones (whiteheads).

Who Should Use Salicylic Acid?

Salicylic acid is generally recommended for individuals with oily or combination skin and those experiencing mild to moderate acne. It is commonly available in over-the-counter formulations at low concentrations, typically between 0.5–2%, to reduce the risk of dryness or irritation.

This topic has been thoroughly investigated, with numerous studies examining the effects of various acids on skin concerns. One such study compared glycolic acid with a combination peel containing salicylic acid in a cohort of 45 patients exhibiting active acne (grades 1 and 2) and post-acne pigmentation. Participants were allocated into two groups of 15: Group A received 35% glycolic acid peels, and Group B received 20% salicylic acid peels. Both groups underwent three-minute peeling sessions fortnightly for 12 weeks, with photographic documentation taken at each follow-up.

The findings indicate that salicylic acid was overall more effective, particularly in diminishing pustular lesions and comedones. It also performed just as well in improving post-acne pigmentation, demonstrating its efficacy in treating both active acne and its sequelae.

Other studies corroborate these findings, such as that by Sekhar V. et al. (2023), which involved 200 patients with acne scarring and hyperpigmentation. In this split-face observational study, salicylic acid peels produced significantly superior responses compared with glycolic acid peels. The authors concluded that salicylic acid is not only effective for acne and hyperpigmentation but also safe for treating melasma, photodamage, freckles and lentigines, especially in darker skin types.

Glycolic and salicylic acids offer similar benefits at lower concentrations, which are available in daily skin care products, such as enhancing skin texture through gentle exfoliation, brightening the complexion, and treating mild acne—making them suitable for home use. However, for more severe cases such as persistent acne, higher concentrations are often required, and research indicates that salicylic acid, owing to its oil-soluble properties, is particularly effective for this purpose.

Whilst both acids confer exfoliation benefits, salicylic acid is more adept at penetrating deeply into congested pores and addressing oily, acne-prone complexions, whereas glycolic acid operates by removing dead skin cells and has proven particularly effective in targeting hyperpigmentation, refining skin texture and offering fine-line reduction through collagen stimulation.

When using these acids at higher concentrations, such as in highly concentrated chemical peels, it is essential to consult a professional to prevent potential skin damage and achieve optimal results. For at-home use, we recommend introducing these acids gradually, performing a patch test, avoiding sun exposure and carefully monitoring your skin's response to maximise their benefits and prevent irritation.

• SHARAD J. Glycolic acid peel therapy: A current review. Clinical, Cosmetic, and Investigational Dermatology (2013).

• ARIF T. Salicylic acid as a peeling agent: A comprehensive review. Clinical, Cosmetic, and Investigational Dermatology (2015).

• GARG V. K. & al. Comparative study of 35% glycolic acid, 20% salicylic–10% mandelic acid, and phytic acid combination peels in the treatment of active acne and postacne pigmentation. Journal of Cutaneous and Aesthetic Surgery (2019).

• MUKOVOZOV I. & al.. Topical AHA in dermatology: Formulations, mechanisms of action, efficacy, and future perspectives. Cosmetics (2023).

• SEKHAR V. & al. Comparative evaluation of glycolic acid and salicylic acid peels followed by PRP for treatment of hyperpigmentation: A split face study. Journal of Dental Specialities (2023).