What Chemical Exfoliants Do to the Skin Surface
Chemical exfoliants use acids or enzymes to break down bonds between dead skin cells, allowing them to shed more quickly than manual scrubs. They target the outermost layer of the epidermis, known as the stratum corneum, to reveal smoother, brighter skin underneath. By accelerating cell turnover, they help unclog pores, reduce dullness, and improve the penetration of other skincare products. Common types include alpha hydroxy acids (AHAs), beta hydroxy acids (BHAs), and polyhydroxy acids (PHAs), each with distinct molecular sizes and skin penetration levels. For a deeper look at how these ingredients interact with skin biology, see the overview from the American Academy of Dermatology at aad.org.
AHAs such as glycolic acid and lactic acid are water-soluble and work primarily on the skin's surface, making them effective for dry or sun-damaged skin. BHAs like salicylic acid are oil-soluble, allowing them to penetrate into pores to clear congestion and reduce acne breakouts. PHAs, including gluconolactone and lactobionic acid, have larger molecules that exfoliate gently without significant irritation, making them suitable for sensitive or rosacea-prone skin. The choice of exfoliant depends on skin type, specific concerns, and tolerance, with concentrations typically ranging from 2% to 10% for at-home products. Regulatory oversight of these ingredients as cosmetics falls under the U.S. Food and Drug Administration (FDA), which defines them as topical agents that affect the body's structure or function without requiring drug approval when used for cleansing or exfoliation.
How Chemical Exfoliants Work at the Cellular Level
At the cellular level, chemical exfoliants disrupt the desmosomes, which are protein structures that hold dead skin cells together. AHAs, for example, reduce the skin's surface pH, which activates enzymes that dissolve these intercellular bonds and promote the shedding of corneocytes. BHAs penetrate the lipid-rich pore lining, dissolving sebum and debris that contribute to comedones and inflammatory acne. This process not only refines texture but also signals the basal layer of the epidermis to generate new keratinocytes more rapidly. The result is a more uniform distribution of melanin, which can fade post-inflammatory hyperpigmentation and sun spots over consistent use.
Key Exfoliating Agents and Their Mechanisms
AHAs and Glycolic Acid
Glycolic acid, derived from sugarcane, has the smallest molecular size among AHAs, allowing it to penetrate deeply and quickly. It is widely used in concentrations of 5% to 15% in serums and peels to stimulate collagen production and improve skin firmness. Lactic acid, found in milk, is milder and also acts as a humectant, drawing moisture into the skin. These acids are commonly formulated in toners, serums, and masks by brands such as Paula's Choice and The Ordinary, which publish ingredient concentration and pH data to guide consumer selection.
BHAs and Salicylic Acid
Salicylic acid, a BHA, is lipophilic, meaning it is attracted to oil, which allows it to enter clogged pores and dissolve the sebum and dead cells that cause blackheads and whiteheads. It is a mainstay in acne treatments and is available in concentrations of 0.5% to 2% in over-the-counter products. The FDA recognizes salicylic acid as a safe and effective topical acne treatment when used as directed. For regulatory context on over-the-counter drugs, visit the FDA's guidance page at fda.gov.