In the vast world of skincare ingredients, glycolic acid is among one of the most common, appearing in everything from cleansers and toners to peels and night creams.
In the first instalment of our acids series, we speak to the skincare experts to find out how it works, what skin concerns it can treat and how beauty therapists can incorporate it into their clients’ routines.
What is glycolic acid?
“Glycolic acid, also known as hydroacetic acid or hydroxyacetic acid, is a 2-hydroxy mono-carboxylic acid – that is, acetic acid with a hydroxylated methyl group,” explains Victoria Evans, education manager for Dermalogica UK.
“It’s also an alpha hydroxy acid, or AHA as it is more commonly known in the skincare industry. Glycolic acid is naturally derived from sugarcane.”
Glycolic acid can also be found in apples, pineapples, papayas, lemons, sugar beet and honey, explains +maskology national trainer Deborah Carrington.
However, it’s common for skincare formulas to contain a bio-identical molecule created in a lab rather than the naturally derived version.
What does glycolic acid do to the skin?
Skin is made up of three layers, with the epidermis at the top, dermis in the middle and hypodermis (or subcutaneous layer) at the bottom. On the surface of the epidermis is the stratum corneum, which protects skin from the environment and prevents transepidermal water loss.
An intact stratum corneum consists of tightly packed layers of dead skin cells that are firmly bonded together. As a chemical exfoliant, glycolic acid is capable of breaking down these bonds, helping to shed dead skin.
Gina Baker, skincare expert and trainer at Germaine de Capuccini, explains, “Our skin cells are held together by positive and negative ionic charges which attract each other and create a glue-like bond. Glycolic acid can cancel some of that charge, which weakens the bond and results in the skin cells becoming loose.”
By loosening the skin cells in this upper layer of skin, “glycolic acid helps to separate and dissolve the desmosomes (a kind of protein) which are the bonds that hold the keratinocytes (old skin cells) together,” explains Evans.
“This will speed up cell turnover, allowing dead skin cells to slough off more rapidly than they would on their own, revealing newer, brighter, and healthier looking skin.”
Glycolic acid’s benefits don’t end there – as well as brightening skin on the surface, it can also work on a deeper level.
“Glycolic acid has the lowest molecular weight of all the acids,” says Maria Naskos, national educator for Xpert Professional, which distributes Italian skincare brand Dibi Milano.
“This means it is small enough to be able to penetrate the stratum corneum to travel into the deeper layers of the dermis.
“Glycolic acid’s size and shape make it a stealthy skin traveller, meaning it can even make its way into hair follicles. Hair follicles play host to sebum and proteins that can contribute to breakouts. Once in the hair follicle, the glycolic acid creates a process of desquamation and chemical exfoliation.”
There is also evidence that glycolic acid supports healthy skin ageing and regular skin tone and skin texture.
Rebecca Jones, trainer and ambassador for Noon Aesthetics, explains, “Glycolic acid stimulates the dermal layer and activates the synthesis of collagen and glycosaminoglycans, equating to volume and youthful skin function.
“It also inhibits tyrosinase, the enzyme that increases colour formation in the skin and is proven to have anti-inflammatory properties along with improving the skin’s natural moisture factor through hydration and ceramide rebalancing.”
What skin concerns can glycolic acid treat?
Glycolic acid is suitable for treating a range of concerns due to the depth it can reach in the skin.
“This acid is considered the gold standard of AHAs,” says Jones. “It’s known for its powerful healthy ageing benefits and ability to smooth fine lines and wrinkles, increase water and lipids and enhance radiance.”
Jones adds, “It can be used to treat skin concerns including hyperpigmentation caused by sun damage, dryness and acne. Because of the increased dermal activity when you use glycolic acid, it helps to prevent scarring. It also helps to minimise pore size and give skin a flawless finish.”
Expanding on glycolic acid’s ability to treat acne and pigmentation, Baker says, “For acne it’s the ideal treatment because it prevents blockages from hyperkeratinisation that form the comedones. With less hyperkeratinisation, the colour intensity reduces, improving dark spots.”
Glycolic acid can also help “rough, dull and tired skin” due to its encouragement of cell renewal, according to Million Dollar Facial founder Jenna Unwin.
If post-acne pigmentation and scarring are a particular concern for your clients, find out more ways to treat them here.
What treatments can glycolic acid be used in?
Glycolic acid is used in a range of professional products and treatments, and particularly ones focused on helping clients achieve renewed, glowing skin.
Naskos says, “When thinking about using acids in non-invasive skin treatments, it is important to understand the pH of the skin. The skin prefers an acidic environment, like vinegar, and the ideal pH for healthy skin is between 4.5 and 5.5.
“In a bespoke facial treatment, a glycolic acid stimulator peel with a lower pH will act as an effective exfoliator to brighten and enhance the skin without any downtime.
“Glycolic acid can also be used in a higher percentage as a chemical peel treatment that will penetrate deeper for visible exfoliation and peeling which will last for a few days post treatment. This should only be done by a qualified professional who can provide pre and post care with the necessary prep and post-procedure skincare if needed.”
“This type of peel is ideal as a bolt-on in many facials, particularly advanced hands-on treatments where product absorption is key, adds Baker. “It’s also a great treatment in a deep cleansing back therapy where congestion may be a concern.”
Glycolic acid products can also be used to boost the efficacy of other professional treatments, although timing is key. Jones explains, “Glycolic acid works in synergy with advanced treatment options such as injectables and radiofrequency, helping to boost and maintain the results.
“However, it cannot be used within the treatment time as it could cause photosensitivity and overstimulation. For the best glycolic acid treatment in clinic, you would choose to have a glycolic peel either as a one-off for a special event or as a course for intensive skin results.”
We asked six pro facialists for their skincare top tips.
How can clients use glycolic acid at home?
Because glycolic acid is a water-soluble ingredient, it can be found in most forms of skincare. The client therefore has a range of choices as to where they incorporate it into their routine, but it’s important that therapists educate their clients about how to use it safely.
Naskos explains, “Use of glycolic acid is down to individual discretion. However, because it’s a very small molecule, it’s rather fast acting – therefore, whichever way clients choose to use it, they should introduce it gradually to build up tolerance in order to avoid irritation.”
Are there any contraindications with glycolic acid?
The fast-acting nature of glycolic acid means that it can be sensitising, but the risk of this depends on the percentage of acid used.
“In most consumer skincare products, you’re unlikely to find a concentration of any AHA, including glycolic acid, above 10%,” says Naskos. “This low concentration means it’s generally safe for skin – anything higher is usually only used by skincare or medical professionals.
“However, any concentration above 12% is not pregnancy or breastfeeding safe.”
People with sensitive skin may be extra prone to reacting to the acid – Jones suggests that people with this skin type “might be better suited to a larger molecular acid”.
If clients have temporary lifestyle factors which increase sensitivity, such as a recent depilation, Baker recommends avoiding glycolic acid altogether.
What ingredients shouldn’t you use glycolic acid with?
Although people may have strict rules about combining ingredients, it really depends on each individual’s skin and the concerns they want to target.
Baker explains, “It’s not so much about avoiding using certain products together but more about the skin you are working on and how those products are applied.
“For example, vitamin C and glycolic acid work extremely well together but sadly it’s often frowned upon. The key here is to minimise irritation.
“For home use, get your client to apply a vitamin C serum in the morning and a glycolic serum at night. Both products will reinforce the collagen production without overstimulating the skin."
“As with all exfoliating ingredients, an awareness of other actives within your regimen should be considered to avoid overprocessing the skin,” adds Evans. Other acids and retinoid use may need to be tempered to avoid skin sensitivity.”
If a client does want to use multiple actives in their routine, Unwin suggests that clients should “always give skin time to settle in between other types of exfoliation if using glycolic acid” to avoid overprocessing.
Which ingredients work well with glycolic acid?
Glycolic acid can be paired with a number of other ingredients depending on the desired skin goal, although this does need to be done carefully. One ingredient which works well with glycolic acid with minimal risk of sensitisation is hydration hero hyaluronic acid.
Carrington says, “A product that is enriched with hyaluronic acid used after the exfoliating effects of glycolic acid will absorb quickly and effectively into the skin, meaning you benefit greatly from the nourishing and hydrating properties of the hyaluronic acid.”
As with any skincare, the most important pairing is SPF. “Glycolic acid does make the skin more photosensitive,” says Baker. “It’s imperative that the client is given the correct aftercare advice on protecting from UV. Ensure that the salon is stocked with a high quality SPF50 that also protects from blue light, pollution as well as UVA and UVB.”
