The Science Behind the Effectiveness of Retinoids
30 November 2023 / 8 minutes read /
Acne is a chronic skin condition that causes pimples, blackheads, cysts, and painful nodules in complex cases. It occurs when skin follicles become clogged with dead skin cells and bacteria, resulting in inflammation. There are a variety of effective treatments for it. However, acne can be challenging to treat from mild to most severe forms. The lesions often reappear after healing, and when they improve on the face, they appear on other body parts such as the back or neck.
With the advent of new skincare products, many brands promise to clear acne using different active principles such as salicylic acid, benzoyl peroxide, or alpha-hydroxy acids. And although the latter may have some effect against blackheads, are they effective in clearing acne once and for all? Let's find out below.
As we have mentioned in previous articles, you must first know what acne is all about to truly understand whether or not an ingredient is effective against their lesions. Acne is a condition involving the pilosebaceous unit of the skin, which is nothing more than the sebaceous glands surrounded by the hair follicle within the dermis. This microscopic structure is highly sensitive to hormones, especially androgens, the reason why acne mainly debuts in the teen years. Even though the above is the norm, acne can persist into adulthood. Indeed, studies show that 26% of women and 12% of men still have acne in their 40s.¹ But let's get to the point.
Acne is caused by four key factors acting together: increased sebum production (facial oil), the cells lining the inside of a hair follicle (hyperkeratinisation), inflammation, and overgrowth of a skin bacterial called Cutibacterium acnes.¹ ² To sum up, the steps necessary for a pimple to come out are as follows:
All of the above occur at the pubertal transition when changes in the body's hormonal milieu alter pilosebaceous gland function. The increase in androgens induces sebum production. At the same time, modifications in the cells of the outermost layer (epidermis) prevent them from shedding easily, clogging the pore shaping microcomedones (mini blackheads), which then enlarge and transform into bigger comedones (blackheads).
Cutibacterium acnes, a common skin germ, inhabits the pilosebaceous unit using lipid-rich sebum as a nutrient source. It, therefore, overgrow in increased sebum environments, further contributing to inflammation.² But acne is not only caused by androgens. Genetics also plays a major role. It has been shown that those with first-degree relatives (parents or siblings) with acne also tend to have it.
Although many products promise and claim to cure acne, the truth is that treatment is based on international recommendations drawn up by expert dermatologists. One of them is the European Academy of Dermatology and Venereology. The academy experts had the same dilemma as we did: with so many cosmetic products on offer today, how do we know which ones really cure acne and which ones don't? ³
Firstly, acne treatment is based on attacking its four key steps, which is why retinoids, azelaic acid, antibiotics, and benzoyl peroxide are mainly prescribed. Second, a distinction must be made between pharmaceuticals that treat the disease and cosmeceuticals.
A cosmeceutical is a topical preparation sold as a cosmetic but with performance features that suggest pharmaceutical action. It can affect the skin positively beyond the time of its application.⁴ But why do we mention this again? Because alpha-hydroxy acids are not considered pharmaceuticals but cosmeceuticals. Therefore, they are not an acne option.⁵ However, its effect can benefit acne-prone skin, which we explain below.
First of all, you must know that according to international recommendations made by an expert panel, alpha-hydroxy acids are not routinely prescribed in acne. They can be used as an adjunct treatment. Alpha-hydroxy acids (AHAs) are a class of chemical compounds based on organic acids found in foods. The most used are lactic acid, mandelic acid, and glycolic acid. The typical indication of AHA-containing products ranges from skin moisturising over wrinkles reduction to deep chemical peels for acne.⁶ Depending on the concentration used, they reduce the coherence of the superficial and follicular corneocytes in the stratum corneum (the outermost layer of skin). Let's talk about the proven effects each one has on the skin.
Most scientific studies talk about glycolic acid when referring to AHAs, so we will focus more on it. Glycolic acid is the simplest alpha-hydroxy acid naturally found in grapes, sugar cane juice, and sugar beets. It is chemically very stable but strongly hygroscopic (attract water in vapor or liquid form from their environment), so it must be kept in closed bottles.⁷ Glycolic acid targets the corneosome, the cell that forms the stratum corneum, and works by dissolving or removing it from the skin. It gradually produces desquamation which helps acne to some extent because it normalizes hyperkeratinization (when cells are generally not shed from the skin's surface).⁸ It can also lower the normal skin pH to a more acidic, preventing C. acnes overgrowth.
Depending on the product concentration, it can lead to three types of peels: very superficial (30%–50%), superficial (50%–70%), or medium-deep (70%).⁹ Lower concentrations of 5%-10% have an extremely superficial action in reducing stratum corneum thickness, but it can change the skin's pH to a more acidic one.¹⁰ However, since low concentrations have subtle effects on the stratum corneum and only modest action on C. acnes by lowering facial pH, no clinical trials have proven that cosmetic products for daily use clear acne, they can only improve it in some way, even similar to a placebo. The reason why dermatologists recommend it as an adjuvant in combination with pharmaceuticals such as retinoids or benzoyl peroxide or as a control treatment once the acne has been cleared. ¹¹
Conversely, higher concentrations effectively decrease corneocyte cohesion, promote epidermolysis, unroof pustules, and affect the follicular epithelium to the level of the sebaceous glands so that it acts at different steps of acne.¹² These peels can range from superficial to deep and are performed depending on the doctor's recommendation in medical settings. Most cause irritation and improve everything from skin texture to post-acne scarring and depigmentation. ¹³ ¹⁴ ¹⁵
Lactic acid (2-hydroxypropanoic acid) is a mild alpha-hydroxy acid derived from sour milk or bilberries.¹⁶ It accelerates epidermis turnover by acting as a chemical peel, and at the same time, it lightens skin by lifting the pigmented cells and increasing the penetration of other active ingredients.¹⁷ These whitening effects may be due to epidermal remodelling and accelerated desquamation, which would result in rapid pigment dispersion. However, lactic acid alone is ineffective in acne, especially inflammatory lesions (pimples). It has been influential on photoaged skin, post-acne scars used as a chemical peel, melasma, and other dermatological conditions.
When used in combination with other ingredients such as niacinamide, glycolic acid or salicylic acid, it can improve acne to some extent.¹⁸ ¹⁹ ²⁰ Even so, we would no longer be talking about lactic acid alone being effective but rather the final solution with all the ingredients. To date, only one study evaluated the preventive power of a 5% aqueous lactic acid solution in 22 patients.¹⁹ ²⁰ Even so, we would no longer be talking about lactic acid alone being effective but rather the final solution with all the ingredients. To date, only one study evaluated the preventive power of a 5% aqueous lactic acid solution in 22 patients.²¹ The patients used the solution twice daily as a cosmetic for an entire year, and although 40% of the patients had fewer pimples at the end of the year, some had relapses and needed antibiotics.Lactic acid, especially sodium lactate, arguably helps keep the skin pH stable, limiting the overgrowth of C. acnes, similar to glycolic acid. However, it is more of a moisturiser than an anti-inflammatory or antibacterial element and therefore has little to do with acne. Only at high concentrations does it act as a chemical exfoliant that does improve the scars and blemishes from acne inflammation.²²
Mandelic acid is an AHA harvested from the extract of bitter almonds via the hydrolysis of benzaldehyde, and its molecule is larger than the glycolic acid molecule. This property gives mandelic acid-specific therapeutic functions. For example, the large molecule of mandelic acid is absorbed very slowly through the skin, making it less irritating, unlike glycolic acid, which is smaller and more rapidly absorbed. Like glycolic and lactic acid, mandelic acid works by superficial peeling and has some keratolytic and antibacterial functions, probably because it keeps the skin's pH acidic.
A mandelic acid-based chemical peel does not cause discomfort (e.g., burning) or redness after use. Desquamation after peeling is both gradual and gentle, meaning that people can undertake their daily activities, which is a plus for mandelic acid.
In terms of its effectiveness, one Polish study showed that 5% mandelic acid cream nightly application for two months reduced the number of inflammatory acne lesions by up to 60%. In addition, it improves skin texture by superficial desquamation when used at 10%, two concentrations typically used in cosmeceuticals. In fact, the study's satisfaction survey revealed that around 80% of patients would like to continue using the cream. Of course, the higher the concentration, the better the effects, including side effects, and the need for a professional to carry out the peeling procedure, so the best results on acne are seen in controlled medical settings.²³
There is no doubt that AHAs are ingredients with properties that benefit acne in one way or another, be it by normalising keratinisation, stabilising pH and in some cases improving sebum production. Acne can leave scars that impair self-esteem and quality of life even after it has cleared up. In these cases, AHA peels are ideal for improving skin appearance, texture, and tone changes after inflammation.
However, although they seem promising, they are not considered pharmaceuticals intended to treat acne, especially in its more acute forms. They remain cosmeceuticals and, in most treatment regimens, are combined with medications targeting acne key factors, such as retinoids, benzoyl peroxide or antibiotics.If you are struggling with acne, you must undergo a dermatological assessment to determine its severity and the treatment you require according to your condition. Our physicians can do that for you. Start your online diagnostics to iniate a treatment request. You will be asked a set of questions and automatically shown a treatment recommendation based on the selected answers.
A physician will review your request and issues an e-prescription if necessary. After the physician’s approval, your treatment is shipped to your home address with complementary 2-day shipping.