How do skin acids work?
“Acids are truly underestimated,” says Professor Briden, who began her career working with the two doctors who first discovered alpha hydroxy acids (AHAs). “They normalize skin cell turnover – 50% of skin problems, including acne, are caused by abnormal skin turnover – plus, they reverse sun damage, stimulate collagen and hyaluronic acid production, and lighten pigmentation.” All of which comes as extra to the peeling properties (dissolving the ‘cement’ that holds the cells together, so dull, flaky cells are shed to reveal fresh, smooth skin underneath) they are famed for.
Which ones work best?
This is where it gets confusing, as with such an extensive menu of peels – from lactic to mandelic, malic to glycolic – it comes down to your skin type or skin problem and the result you want to achieve.
“AHAs are good to peel thicker or sun-damaged skin,” says Professor Briden. “They have a smaller molecule and so penetrate the skin, which is why you often feel that tingle. But even at a lower concentration of 5% acid, you’ll still get results. However,” she warns, “these are not for you if you have rosacea or sensitive skin.”
Mandelic acid, derived from almonds, is good for balancing acne and calms rosacea “due to its antibacterial and calming properties. It’s also good for pigmentation,” says Briden.
Polyhydroxy acids (PHAs) are second-generation acids that offer a smoother, tingle-free path. They are less penetrative and so don’t sting, plus they are hydrating, making them excellent for dry skin while still giving a gentle peel. “They are also a potent antioxidant, inhibiting the enzyme that destroys collagen,” says Professor Briden. They also protect against glycation – the hardening of collagen fibers by excess sugar – and treat eczema, which makes them perfect for all-round regular use.
“Beta hydroxy acid (BHAs) including salicylic acid are mainly used to treat acne- and breakout-prone complexions as they have such good anti-inflammatory properties,” says Briden. “But you wouldn’t make these a part of your normal regime unless you had problematic skin, as they are so dehydrating.”
The ideal peeling regime
We may associate a good AHA peel with that pleasing skin tingle, but any product (peel or otherwise) that triggers this reaction should not be an ongoing part of your regular daily regime. “We use the AHAs when we want more of a peel, so as a weekly mask, if you’re starting out on a new regime, or to treat sun damage,” advises Briden. They also freshen up post-summer or post-winter skin. “In the same way that micro-needling or micro-dermabrasion create an ‘injury’ to induce skin repair, the tingle and redness is creating a similar skin response and this is not something you want to do long term, only as a short course or booster treatment. The pH of your glycolic peel plays a role, and the lower it is, the more irritating it is. So, for daily or ongoing use, choose pH3.5 to 5.5.’
Alternatively, Briden recommends using PHAs or a 3-5% AHA as a daily staple: “They moisturize and give antioxidant protection, repair the skin barrier, normalize skin turnover boost collagen and still give a peel.”