We have touched upon the concept of peeling before, noting the difference between the physical type such as scrubs, and the chemical type.
Chemical peels can be loosely categorised in AHA (Alpha Hydroxy Acids) and BHA (Beta Hydroxy Acids), which have different effects and benefits. Let’s see them together:
Alpha Hydroxy Acids
These acids work on the outermost layer of the skin, breaking down the bond between skin cells of the epidermis. With their loosening, the skin cells start shedding at a faster rate, and the underlying layer is consequently exposed. With a tighter stratum serving as a base, the skin appears overall healthier, make-up sits better and you avoid the “cakey” effect.
AHA acids are water-soluble, stimulate collagen production and may also provide hydration (see lactic acid).
There are many sub-categories of AHA acids. Here are a few:
1. GLYCOLIC ACID
A sugarcane-derived AHA, glycolic acid has been revered by many professionals as the best-performing of its family. Thanks to its low molecular weight, glycolic acid can penetrate the skin the deepest and the fastest, stimulating collagen production, thus better promoting deeper wrinkle reduction.
In addition, glycolic acid is also effective at reducing photodamage, which makes it ideal for those with more mature skin.
Dry skin may also benefit from this particular chemical peel given it also aids in drawing moisture to the skin, preventing transepidermal water loss.
Those with sensitive skin should be cautious though as the quick penetration of the molecule may cause irritation.
2. LACTIC ACID
Lactic acid is another naturally occurring acid, and its name hails from the most common source of it: sour milk.
Like glycolic acid, lactic acid exfoliates and helps bring moisture to the more superficial layers of the skin. This, in turn, improves resistance to external agents which may dry out the epidermis and cause flakiness.
Like all AHAs, lactic acid is great for general exfoliation and skin brightening; however, the larger molecule does not penetrate the skin layers as quickly and deeply as glycolic acid. For this reason, it is often preferred over glycolic acid by those with sensitive skin as it causes less irritation without losing the benefits.
Some studies show that it also helps reduce the appearance of fine lines and wrinkles alongside clearing sunspots by accelerating cell turnover and directly inhibiting melanin production.
3. MANDELIC ACID
Mandelic acid is a naturally occurring acid derived from bitter almond and wild cherry.
It helps address fine lines, firmness, acne and discoloration, making it a truly polyfunctional product. Its larger molecule is better suited for sensitive skin types and for skin types with higher concentrations of melanin because it doesn’t trigger post-inflammatory responses or pigmentation like we see from other AHAs. Mandelic acid also has antimicrobial properties which helps fight acne and clogged pores.
4. MALIC ACID
Malic acid, much like previous AHAs we examined, is also found in nature, specifically in fruit. One such example is apples, rich in this AHA, and original source of its name (apple is “malum” in Latin).
Much like its sibling AHAs, it helps with skin turnover, improves the overall appearance of it, helps diminish wrinkles & fine lines, whilst also acting as a humectant. What is most interesting is how it is also utilised for balancing the skin’s pH level as Malic acid is more balanced than other fruit acids.
Though your skin may have a higher tolerance level to Malic acid, it is still recommended you patch test it first in order to gauge how your skin reacts to it.
5. TARTARIC ACID
Tartaric acid is a naturally occuring AHA found mainly in grapes and tamarinds.
It boasts powerful antioxidant properties alongside the aforementioned positive effects of all other AHAs.
Interestingly, Tartaric acid crystallises into a transparent form when extracted from its source which, in turn, is believed to make it more unstable compared to other AHAs but when used in tandem with other acids (see salicylic), it can actually help stabilise other compounds.
6. CITRIC ACID
The name is a dead giveaway of where you can find this acid: citrus fruit.
Whilst it acts as any other AHA with all the skin turnover benefits, it also helps improve shelf-life of other products by stabilising their pH.
More importantly, it can cause irritation in those with more sensitive skin, hence why more gentle exfoliators are to be preferred.
Beta Hydroxy Acid
BHAs work by penetrating deeper into the skin thanks to their characteristic of being lipid-soluble, meaning they bypass oil-based gunk and debris, cleaning out pores from the inside. It also helps reduce signs of aging by exfoliating the epidermis, exposing healthier layers and lessen the appearance of wrinkles and fine lines.
Arguably the most well-known acid, salicylic acid is a naturally occurring BHA derived from willow bark.
It is renowned for not only dissolving dead skin cells on the surface of the skin, but also being able to get down into the pore, dissolve the oil, and break apart the debris inside that commonly leads to acne.
This makes it extremely popular amongst those who are acne-prone. When used regularly, it also prevents new acne and blackheads from forming by keeping debris and inflammatory agents well clear of the skin. Additionally, it can correct dark spots without irritation thanks to its topical anti-inflammatory benefits; this renders it suitable for those who suffer from hyperpigmentation as well.
However, not all acids are perfect and while BHA has been shown to be mildly antibacterial, it has not been shown to kill p. acnes bacteria, the most common bacteria that leads to acne. For this reason, salicylic acid is often paired with antibacterial ingredients or benzoyl peroxide for the best results. Salicylic acid can also be mildly drying to the skin, so it’s important to moisturize when using it. Generally speaking, dermatologists often recommend a salicylic acid formulation that contains 0.5% up to 2%.
LHA or Liphohydroxy acid is an acid first developed in the 1980s by L’Oréal. It is a derivative of salicylic acid, and acts in a more gentle manner than its parent due to it being more lipophilic. This results in slower chemical activity and a gentler exfoliation experience.
It still effectively promotes deep pore cleansing and skin rejuvenation properties.
Studies have also shown that LHA appears to have antimicrobial, anti-inflammatory, anti-fungal and anticomedogenic properties, combating acne and even dandruff!
Polyhydroxy acids, which have been called the “new generation of AHAs,” have become more widely known in recent years. This group includes acids such as gluconolactone, galactose and lactobionic.
They work in a similar manner to AHAs but also possess antioxidant properties, meaning they can help protect skin against free radical damage.
Because of their larger molecule size, PHAs don’t penetrate skin as deeply as AHAs, making a staple amongst those with even the most sensitive skin.
PHAs have been shown to boost the benefits of other treatments when used in tandem with retinoids to improve acne, with hydroquinone to improve discoloration and with lasers and microdermabrasion to enhance post-procedure results.
How to Use Hydroxy Acids
While using hydroxy acids is common and generally safe for your skin, it is also important to follow certain guidelines in order to not overdo it, especially in the first stages of using these great little helpers:
- Do a patch test. Apply a small amount on the arm and then on the forehead (where the facial skin is the thickest) to see how your skin will respond.
- Start slow. In general, when using acids, always start conservatively with a lower concentration and then work up to see what your skin can tolerate.
- Use a daily sunscreen. Studies show that AHAs make skin more sensitive to UV radiation while using the products and for weeks after discontinuing use.
- Consult your dermatologist. It is not uncommon for people to experience mild redness and peeling when first beginning an AHA/BHA skin care regimen. If persistent irritation or redness occurs, consult a doctor.
- If you’re pregnant, beware. Speak to your GP before incorporating acids into your routine. Some acids, specifically salicylic acid, should not be used during pregnancy.
Whatever your skin type, tone or condition, there is so much research behind hydroxy acids supporting their numerous benefits. All you have to do is understand what your skin needs the most and try different variants until you find the perfect fit for your skin.