Ever Wondered How To Layer Skincare Acids? Here's How
Strap in for a crash course in beauty chemistry as Ashleigh Cometti uncovers the benefits of acids and why they're the key to glowing, radiant skin
Learning the ins and outs of skincare often feels like you need a PhD. Even more so when it comes to acids, with their scientific sounding names that seem better suited to a laboratory than your bathroom cupboard.
But these skincare MVPs need not be feared — when used properly they can pave the way to a glowing, radiant complexion.
Acidic skincare is a broad category, with some forms drenching skin in hydration (we see you, hyaluronic acid), while others are especially efficient at ridding the skin of the dead cells that cause dullness and uneven skin tone.
There are the usual suspects — hyaluronic, salicylic, ascorbic — but throwing some of the lesser-known acids into the mix like mandelic, tartaric and malic is enough to send anyone into a Google search frenzy.
We enlisted the help of five skincare experts to find the acids that should feature in your skincare line-up, and how best to use them.
Most skincare acids can be categorised into two prominent acid families — alpha hydroxy acids (AHAs) and beta hydroxy acids (BHAs).
As a trained medical doctor, former professor of dermatology and the head of research and development for exclusive French skincare line Biologique Recherche, Dr Philippe Allouche is well-versed in skincare acids and their benefits to skin.
Dr Allouche breaks down the distinction between AHAs and BHAs by explaining how the molecular structure between the two differs, meaning each is absorbed differently by the skin.
“Alpha hydroxy acids are small molecules derived from fruit sugars or milk with exfoliating power,” Dr Allouche says. Think malic acid, citric and lactic acid.
“Their small size allows them to penetrate deeper into the first cell layers in order to break the bonds between corneocytes [the outermost part of the epidermis] and facilitate the natural exfoliation of the skin,” he says.
He adds that the effects of AHAs on the skin also differ depending on their concentration — at a low concentration AHAs help to moisturise the skin because they stimulate the production of amino acids (which in turn keep it hydrated). Highly concentrated AHAs have keratolytic effects, meaning they exfoliate and smooth the skin.
At the other end of the spectrum are beta hydroxy acids (BHAs), like salicylic acid.
“Beta hydroxy acids are more liposoluble [fat or oil soluble] than alpha hydroxy acids, which will allow them to be more easily inserted into the pores of skin and give them purifying properties,” Dr Allouche says.
BHAs have anti-inflammatory and antibacterial properties, which render them an excellent option for oily or acne-prone skin.
There’s a third hydroxy acid to familiarise yourself with too, says Elizabeth Arden field sales and education manager Rebecca Hollowood — polyhydroxy acids (PHAs).
“Polyhydroxy acids are the second generation of AHAs. Due to their gradual penetration into the skin, PHAs exfoliate in a milder manner. PHA molecules also attract water molecules, which in turn moisturise your skin,” she says.
So, you’ve scored yourself an A+ on hydroxy acids. But how well do you know your lactic from your mandelic? Your glycolic from your citric? Put your knowledge to the acid test with our handy guide.
What is it? Ascorbic acid (also known as L-Ascorbic acid) is a form of vitamin C and works to protect skin from free radical damage. It inhibits melanin production, lightening pigmentation and reducing dark spots.
Best for: All skin types.
Commonly found in: All skincare.
Pros: Unlike other acids, ascorbic acid is not an exfoliant, and helps to even out skin tone and boost radiance.
Cons: Ascorbic acid is highly unstable, and begins to oxidise as soon as it's exposed
to air. It works best when fresh, so ensure your product pick factors this in. An amber bottle with a dropper is your best bet.
Try it: NIOD Ethylated L-Ascorbic Acid 30% Network, $120.
What is it? “Hyaluronic acid is a non-exfoliating acid and is found naturally in the body and skin,” says Caci skincare trainer Linda Sharrem. “Its function is to draw and bind water to the skin and keep the skin plump.”
Best for: All skin types.
Commonly found in: All skincare.
Pros: Hyaluronic acid’s humectant properties work wonders on dry and dehydrated skin, helping to protect against trans-epidermal water loss. It also layers easily with any other acid.
Cons: “If you are prone to puffiness, high doses of hyaluronic acid can create more puffiness as it draws more water to the area, so be wary of this,” Sharrem advises. Try it: Elizabeth Arden Hyaluronic Acid Ceramide Capsules Hydra-Plumping Serum, $168.
What is it? A powerful AHA that helps improve radiance, and reduces the appearance of fine lines, wrinkles and pores.
Best for: Ageing or acne-prone skin.
Commonly found in: Toners and serums.
Pros: The exfoliating agent helps to leave skin brighter and more hydrated, and is a great jump-off point for those wanting to start peels.
Cons: As the smallest of all AHAs (in terms of molecular weight), it penetrates deeply into the living part of the skin’s epidermis and can be irritating. For this reason, glycolic is best suited to experienced skincare acid users.
Try it: YSL Pure Shots Perfect Plumper Cream, $145.
What is it? Citric acid is an AHA with skin exfoliating benefits due to its comedolytic [anti-acne] and keratolytic [skin-softening] properties.
Best for: Oily or acne-prone skin.
Commonly found in: Cleansers and serums and as a pH adjuster or a preservative in foaming products.
Pros: Citric acid’s astringent properties mean it works well to refine the skin surface and brighten the complexion, while dialing down inflammation and redness.
Cons: Being too heavy-handed with citric acid can lead to skin stinging and burning.
Try it: Glow Lab Age Renew Resurfacing Cleanser, $20.
What is it? More antioxidant than acidic, plant-derived ferulic acid helps protect the skin from free-radical damage, and works well when combined with vitamin C and E.
Best for: Ageing skin.
Commonly found in: Treatments and serums.
Pros: Ferulic acid is also a popular pick for its ability to reduce the appearance of lines and wrinkles.
Cons: Because of its origin, some people with a sensitivity to gluten (oats or bran) may experience an adverse skin reaction.
Try it: Biologi Bf Restore Face and Body Serum, $83.
What is it? This hydrating AHA helps to exfoliate dead skin cells, revealing a more radiant complexion. It also helps to reduce the appearance of fine lines, wrinkles and dark spots.
Best for: Acne-prone skin.
Commonly found in: Peels and serums.
Pros: “At a low pH, lactic acid is an exfoliating agent; it increases the elimination of dead cells and improves cell renewal. At a higher pH, it is a hydrating agent,” Dr Allouche says.
Cons: Overusing lactic acid or using a high concentration can lead to skin irritation, Hollowood warns.
Try it: Codage Peeling Lotion, $115.
What is it? “Mandelic acid is a water-soluble AHA that offers superficial exfoliation,” says Nafisah Abdalla, science communications associate manager at Deciem. “It does so by targeting the outermost layer of the skin and promotes its shedding.”
Best for: Mandelic acid’s high molecular weight means it’s a milder form of exfoliation, so is good for first-time users of topical acids.
Commonly found in: Moisturisers, serums, toners and masks.
Pros: It helps to regulate sebum production, unclogging pores and reducing inflammation, which can result in fewer breakouts.
Cons: Mandelic acid is tolerated well by most skin types but if sensitivity occurs (redness, swelling or irritation), cut back to using every other day.
Try it: Environ Tri BioBotanical Revival Masque, $105.
What is it? Tracey Pedersen, national education manager for Clinique, counts salicylic as her favourite acid for its exfoliating properties. “Salicylic acid is used in skincare to release dead, dull cells. It can also be used to treat dryness and fight bacteria,” she says.
Best for: All skin types, but works well on oily or acne-prone skin.
Commonly found in: Serums, cleansers, moisturisers and spot treatments.
Pros: The superficial exfoliant has purifying properties to smooth imperfections and fight against blackheads, ingrown hairs and dandruff.
Cons: Salicylic acid may irritate the skin if used in a too-high concentration.
Try it: Clinique Even Better Clinical Radical Dark Spot Corrector + Interrupter, from $134.
What is it? This organic acid can be found in nature from fruit sources, namely grapes, bananas, tamarinds and citrus, Sharrem says.
Best for: Ageing or acne-prone skin.
Commonly found in: Peels, masks, cleansers and pore treatments.
Pros: Tartaric acid offers optimal exfoliation as it reaches different layers of the dead skin cells, and stimulates collagen production within the skin. Its antioxidant properties make it an ideal option for skin in need of wound healing, and also has an anti-ageing effect.
Cons: This AHA can increase your sensitivity to the sun, so applying SPF daily is a must.
Try it: Skinsmiths Overnight Glow, $58.
What is it? Similar in structure to citric acid, this mild AHA is found in unripe apples, and fruit including grapes, watermelon, and cherries, along with carrots and broccoli, Sharrem says.
Best for: Sensitive skin.
Commonly found in: Masks, at-home treatments and serums.
Pros: Malic acid helps to hydrate and brighten skin, unlike other harsher acids that can impact the skin’s lipid barrier.
Cons: Although gentler than other acids on this list, a patch test is still recommended in case of sensitivity.
Try it: Murad Replenishing Multi-Acid Peel, $145.
A LESSON IN LAYERING
When it comes to adding acids into your skincare regime, it's a good idea to see a trained therapist.
If products are layered incorrectly, you risk causing adverse reactions like redness, sensitivity and other skin irritations.
Abdalla advises to only incorporate one exfoliating acid into your skincare regime to avoid the risk of over-exfoliation. “We recommend avoiding combining direct acid formulations with other direct acids and retinoids in a regimen. We consistently advise users to build up skin tolerance by beginning with low concentrated formulas, and working their way to higher percentages gradually,” he says.
“The likelihood of developing a compromised skin barrier can be lessened by using formulations with lower concentrations of acids as a means to preparing the skin for chemical exfoliation. Overuse of any direct acid without the appropriate level of skin tolerance will lead to increased chances of developing a compromised barrier, making the skin more susceptible to developing additional skincare concerns.”
If you’d rather not layer, consider purchasing one product that has a combination of acids, as the ingredients have been formulated to work harmoniously.
There’s one thing our skin experts all agree on, if you’re going to use acids then SPF is a must — remember to protect your skin and your results.