Lactic Acid

Alpha Hydroxy Acid

Also known as: 2-Hydroxypropanoic acid, AHA

Description

Lactic acid is an alpha hydroxy acid (AHA) with a larger molecular weight (90.08 Da) than glycolic acid (76.03 Da), resulting in slower, more even penetration and generally better tolerability. Beyond its exfoliating properties, lactic acid uniquely functions as a humectant and stimulates ceramide synthesis in the stratum corneum. It is a component of the skin's natural moisturizing factor (NMF) and promotes epidermal turnover, improves skin texture, reduces hyperpigmentation, and strengthens the barrier. [Smith 1996]

Mechanism of Action

Lactic acid decreases corneocyte cohesion by disrupting ionic bonds between cells in the lower stratum corneum, promoting desquamation. It inhibits tyrosinase activity, contributing to its depigmenting effect. Lactic acid stimulates the production of ceramides (particularly ceramide 1 linoleate) in the epidermis, enhancing barrier function. At pH 3.5–4.0, it also exhibits humectant properties by attracting and retaining water in the stratum corneum. At higher concentrations, it increases dermal glycosaminoglycan and collagen synthesis. [Rawlings 1996]

Indications

  • Keratosis pilaris [Smith]
  • Mild to moderate acne [Rawlings]
  • Post-inflammatory hyperpigmentation [Smith]
  • Melasma [Smith]
  • Photoaging / fine lines
  • Xerosis / dry rough skin
  • Ichthyosis vulgaris
  • Uneven skin texture

Available Concentrations

2%5%10%12%30% (professional peel)50% (professional peel)

Side Effects

  • Mild stinging or burning on application [Smith]
  • Erythema [Smith]
  • Dryness and peeling
  • Increased photosensitivity
  • Irritant contact dermatitis at higher concentrations

Contraindications

  • Known hypersensitivity to AHAs [Smith]
  • Active herpes simplex lesions (for peels)
  • Open wounds or severely compromised skin
  • Use with caution alongside retinoids or other exfoliants

Pregnancy Category

Generally considered safe at low OTC concentrations (≤10%); professional peels not recommended

Found In

Cosmetics containing Lactic Acid

Chemist at Play 5% AHA + 1% BHA Body LotionChemist at PlayDot & Key Blueberry Hydrate 12% Barrier Boost SerumDot & KeyFixderma Nigrifix Cream (for Hyperpigmentation)FixdermaHyphen Brightening Face Serum 5% Niacinamide + 1% Alpha ArbutinHyphenJessner's Solution Peel (Lactic + Salicylic + Resorcinol)Generic / Compounding PharmacyMinimalist 2% Alpha Arbutin Serum + Hyaluronic AcidMinimalistMinimalist Multi Peptide Night Face SerumMinimalistMinimalist 2% Salicylic Acid SerumMinimalistPilgrim 25% AHA + 2% BHA + 5% PHA Peeling SolutionPilgrimPlum 5% Niacinamide & Rice Water Beginner Friendly Face SerumPlumYellow Peel (Retinol 5% + Lactic + Ascorbic)Dermatology-grade

Related Conditions

Keratosis Pilaris First-line keratolytic — dissolves keratotic plugs and smooths follicular papules Acne Vulgaris Exfoliant — promotes desquamation and reduces comedone formation Melasma Depigmenting agent — inhibits tyrosinase and promotes turnover of melanin-laden keratinocytes Photoaging Anti-aging exfoliant — stimulates collagen and GAG synthesis, improves fine lines and texture Xerosis Humectant and ceramide booster — enhances hydration and restores barrier lipids

References

  1. Rawlings AV, Davies A, Carlomusto M, et al. "Effect of lactic acid isomers on keratinocyte ceramide synthesis, stratum corneum lipid levels and stratum corneum barrier function." Arch Dermatol Res, 1996. doi:10.1007/BF02505107
  2. Smith WP. "Epidermal and dermal effects of topical lactic acid." J Am Acad Dermatol, 1996. doi:10.1016/S0190-9622(96)90613-0

Limitations

This page provides a general overview of Lactic Acid in dermatology. It does not cover every possible use, formulation, or interaction. Individual responses to compounds vary — what works for one person may not work for another. Always consult a qualified dermatologist before starting or changing any treatment.