With its ability to work on wrinkles, dead skin cells and skin’s moisture levels, lactic acid is a great all-rounder for any skin type, but particularly acne-prone complexions
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If someone told you that slathering your skin in sour milk could wither away spots, buff away dead cells and improve the look of fine lines, you’d probably think it was some sort of bizarre TikTok hack. Yet, bathing in goat's milk was the secret to Cleopatra's legendary smooth skin as far back as Ancient Egyptian times. Fast forward to 2022 and, apart from giving dairy products their distinctly tart odour, what exactly is lactic acid's role in the beauty space?
What is lactic acid?
“Lactic acid is an organic acid that occurs naturally in the human body,” says Ann-Marie Ronlund Jensen, brand manager at Nuori skincare. “In skincare, lactic acid is a colourless, syrupy liquid that’s classified as an exfoliating alpha-hydroxy acid (AHA).”
Extracting the ingredient involves a complex fermentation process, typically using diary products and, in Nuori’s case, carbohydrates. “Naturally-occurring sugars such as lactose in milk undergo a process in which microorganisms break down or alter the compounds resulting in more potent ingredients,” Ronlund Jensen explains.
What are the benefits of lactic acid for your skin?
First and foremost, lactic acid is beloved for its exfoliating properties, which directly affect hyperpigmentation and acne. “Lactic acid gently breaks the bonds that glue dead cells to the skin’s surface; in doing so it unclogs pores, stops acne from evolving and helps to fade post-breakout dark marks,” says Ronlund Jensen.
A study published in the Journal of the American Academy of Dermatology also found that a 12 per cent concentration of lactic acid penetrated both the dermis and epidermis (five per cent could only reach the top layer of skin), resulting in thicker skin and fewer wrinkles.
In skincare, lactic acid is a colourless, syrupy liquid that’s classified as an exfoliating alpha-hydroxy acid (AHA)
Ann-Marie Ronlund Jensen, Nuori skincare
How does lactic acid differ from other acids?
Where lactic acid differs from all the other alpha-hydroxy acids out there is its ability to bind moisture to skin. “Lactic acid is a humectant and part of the natural moisturising factor (NMF), which supports the skin barrier,” says Ronlund Jensen.
Another point of difference is the size of its molecules. Lactic acid is made up of large molecules so it can’t penetrate as deeply as say glycolic acid but is still effective at exfoliating the top layer of skin. This is good news for those with sensitivity and dark skin tones, which are more prone to post-inflammatory hyperpigmentation when exposed to harsh exfoliants. “Both will be able to tolerate lactic acid better, especially as it is more moisturising than other AHAs,” says Stanislas Le Bert from L:A Bruket, which uses lactic acid to adjust the pH of its skincare formulas. “This ensures the preservation of the skin's microbiome, improves its barrier performance and enhances its healthy appearance.”
That said, the usual rules for AHAs applies: introduce lactic acid into your skincare routine slowly and apply an SPF30 plus during the day.
More from beauty and skincare: Skincare Science: The best hyaluronic acid serums for a plumper, more vibrant complexion
