If we took a peek at times gone by, we’d realise that the use of exfoliating acids in skin care is nothing new. Cleopatra, Queen of Ancient Egypt regularly bathed in donkey’s milk, now known to be rich in lactic acid, while French women used aged wine that contains tartaric acid. Personally, I find chemical face peels quite harsh on the skin and I believe that the benefits they offer can be obtained by other means, but never the less they are very popular. Therefore, as quite a few of you have asked for my opinion on the matter, I’ve prepared a quick guide with their properties, dosage and uses.
HOW DO THEY WORK
Chemical face peels are exfoliating acids that alter the pH of the skin, causing the cellular interconnections of the corneocytes (mature cells) to breakdown and come away, accelerating their elimination. As a result, the basal layer of the skin (the innermost layer of the epidermis) accelerates its tissue renewal process.
Found in foods, especially in citrus fruits. Lemons are particularly rich in this acid and can contain up to 8% dry matter content. This means that each litre of squeezed lemon contains up to 47g of citric acid. Its action is mainly keratolytic.
Releases gluconic acid, which promotes exfoliation and cell renewal and modulates the keratinization process. It also has good antioxidant and restorative capabilities, making it ideal for use on a damaged skin barrier. It is an exfoliant with excellent moisturising properties and as it is naturally present in the skin also, it helps with cell renewal. Much gentler than other hydroxy acids, it is usually combined with other exfoliating agents (in particular, Alpha-hydroxy acids) to make a face peel product less irritating on the skin.
Obtained from natural sources such as fruits, beets and sugar cane. The level of exfoliation produced is usually very superficial and even without removing the product, the probability of skin irritation is relatively low. As chemical face peels go, this one provides very fast exfoliation (light molecule, low molecular weight, easily absorbed by the skin).
- Glycolic acid stimulates the synthesis of collagen, hyaluronic acid, mucopolysaccharides.
- Has excellent exfoliating properties at a concentration between 10 and 15% and is therefore used in the treatment of acne, psoriasis and keratosis.
- In higher concentrations (15-70%), this exfoliating acid is used to treat fine lines, stretch marks and hyperpigmentation.
Common side effects:
Redness, dermatitis, tingling, erythema, and skin sensitisation.
Lactic acid has properties very similar to those of glycolic acid, with the added benefit of being more economical and better skin compatibility. It is one of the chemical face peels that naturally acidifies the surface of the epidermis. However, it has never achieved the same commercial success as that of glycolic acid, which is far more popular in skin care products. It promotes skin softness, hydration, luminosity and elasticity, but more investigation is needs to confirm whether or not it’s able to stimulate the synthesis of ceramides, and thus increase the skin’s barrier function.
- Used as an exfoliating agent in the treatment of dandruff, keratosis, warts, calluses and acne.
- Normally combined with other exfoliating agents to counteract dry, cracked skin.
- Used in feminine hygiene products.
Common side effects:
Redness, dermatitis, and skin sensitisation.
This acid is formed by combining gluconic acid, a polyhydroxy acid, and a sugar molecule, (galactose). Due to its relatively high mass and the way it reacts to moisture, the exfoliation obtained is very superficial and light.
- Remarkable repairing and healing activity, typical of galactose, a sugar that plays a key role in the synthesis of collagen.
- It has a very powerful antioxidant action.
- Brightens and softens the skin. It is much gentler than other hydroxy acids.
- Promotes cell renewal by regulating keratinization.
- Used as an anti-ageing treatment.
- Given its delicate action, it is used on sensitive skins.
An alpha-hydroxy acid (AHA) that comes from fruit, especially apples. Combined with other AHAs, it provides very good keratolytic activity – It causes mature cells to break away faster and reduces the thickness of the stratum corneum. This enables the rapid elimination of pigmented cells, increasing skin luminosity. Can also be applied to skin suffering from cystic acne, as it causes the skin lesions to drain.
Mandelic acid was first used in skin care products about fifty years ago, and it was an instant hit. So much so that, today, it is one of the most common used ingredients in formulas designed to lighten and exfoliate the skin. The name “mandelic” derives from the word “mandel” which in German means almond.
For me it is one of the chemical face peels that sits between glycolic and salicylic (it’s stronger than glycolic acid but not as strong as salicylic acid). In most cases, there are no side effects like burning or tingling immediately after applying it, which is why it’s often recommended for sensitive skin types. This exfoliating acid can also be applied before sun exposure as it’s not photosensitive.
- It is mainly used in the treatment of acne.
- Also useful in the treatment of blackheads, skin discoloration, dry cracked skin, fine lines and rosacea.
Much stronger than glycolic acid and salicylic acid.
- Powerful keratolytic activity, used in the treatment of skin imperfections.
- Rapid elimination of pigmented cells that increasing skin luminosity.
- Thanks to its lipophilicity, it penetrates deep into follicles where it has a bacteriostatic and comedolytic effect, causing cysts and microcysts to drain.
- It also has a sebostatic effect on skin.
(Derived from retinol) The acid form of vitamin A. The exfoliating action of retinoic acid is known to repair and normalise capacity of the skin. However, like tretinonine, retinoic acid is a known teratogen in high doses, even long after treatment ends. Its use is prohibited during pregnancy and breastfeeding.
- Promotes cell renewal, hydrates the skin and keeps it softer for longer.
- This chemical face peel is usually formulated together with depigmentation active ingredients.
- It can be used to treat fine lines.
- Maintains the integrity and functionality of the skin.
A beta-hydroxy acid (BHA) derived from the enzymatic hydrolysis of salicin, a salicoside glycoside extracted from the Salix alba (willow) plant. It is a stronger acid than those previously mentioned in this article. As it’s soluble in oil and in skin lipids, it can easily penetrate the stratum corneum and the inside of sebaceous ducts. It’s also a good antimicrobial.
- Used in skin care to prepare superficial skin peels designed to treat mild or moderate pustular acne.
- Can quickly penetrates inflamed lesions, killing off bacteria and soothing skin.
- Exfoliating effects guaranteed even at very low concentrations (1-2%).
- Also used in the treatment of melasma and post-inflammatory hyperpigmentation.
- During the entire treatment period (4-6 sessions, separated by at least 3 weeks), it is strongly recommended to avoid sun exposure.
Common side effects:
The exfoliating effect can be very evident, sometimes causing the appearance of dark spots (that spontaneously disappear after a few days). It should not be administered to those who are allergic to salicylates.
Tartaric acid is another alpha-hydroxy acid found in fruit and is particularly abundant in grapes and tamarind. It is mainly used in skin lightening products, designed to treat melasma. It is also used in anti-acne, anti-aging products and is used in the treatment of impure, blocked or thickened skin. Another notable property is its ability to regulate the skin’s pH. It is generally used in concentrations between 1 and 10%, alone or combined with other alpha-hydroxy acids.
(Derived from retinol) Used in dermatology as an exfoliant in the treatment of post-inflammatory hyperpigmentation. It is usually used in very low concentrations (0.05-1%). Offers long term visible effects (6 months or more after treatment).
TRICHLOROACETIC ACID (TCA)
Used only in dermatology for the treatment of warts, skin discoloration, post-acne and post-surgical scars, rosacea, medium-severe photoaging, melasma, sun spots, keratosis.
It is used in concentrations that range between 10% and 40% depending on the type of peel to be performed (10-25% for a superficial peel, 30-40% for a deep peel). Depending on the concentration used, skin can take anywhere between 3 to 15 days to regenerate. After treatment, stinging, burning, hyperaemia, redness, swelling and erythema may occur.