Active ingredients such as hydroxy acids, retinol or vitamin C sometimes sting or redden the skin. We asked several experts if it was an indication of its effectiveness.

More and more people say they have sensitive skin: 50% of the European population, according to the Spanish Academy of Dermatology (AEDV). And although sensitivity can occur for many reasons, such as genetic or environmental ones, it is the products of topical application that is the most indicated. I mean cosmetics. Now, one thing is that a serum, for example, feels terrible to our skin because it is altered or has some pathology (atopic skin, eczema, psoriasis, etc.), and another is that a particular desired reaction occurs to obtain a specific result. : regenerate, gain luminosity, fade spots or reduce wrinkles.

So, from the outset, worrying about the fact that with certain ingredients, we notice that it changes a bit does not make sense, although we must be clear in which cases and what we are perceiving. Aina Bordoy, from Bonnin Pharmacy, explains it. “It is normal to feel irritation, redness or itching when applying certain cosmetic products. This is because some active ingredients, such as alpha hydroxy acids or some forms of vitamin C, must be formulated at an acid pH to ensure their effectiveness and absorption, while the skin’s pH under normal conditions is slightly acid (between 4 .7 and 5.7). In the case of transforming active ingredients (such as retinol or hydroxy acids), there is an increase in cell renewal, leaving the skin more exposed and causing this irritation or itching, which will be greater as the concentration of the active ingredient increases”. What happens to the skin when a product sting is that it enters into an inflammatory process in the deep layers, which will subside when cell regeneration and the synthesis of collagen and elastin startup.

Transformative assets

If we talk about retinol, we make it a transforming ingredient that accelerates renewal and is capable of unifying the tone, reducing expression lines and improving texture. “At the time of applying it to the skin, it is very well tolerated, but if we do it several days in a row, after a week we will have retinoid dermatitis because it is cumulative. To reduce this reaction, it is possible to start with low concentrations and with retinol derivatives or combined with other molecules, progressively retinting the skin until reaching the necessary tolerance. For example, every three nights the first two weeks”, explains Aina Bordoy.

And what is the correct percentage? Marta Hermosín, a specialist in dermo-cosmetics at the Institute of Comprehensive Dermatology, recommends starting at 0.025 for virgin skin and stepping up to 0.2 two days a week until doing it every other day, ending at 0.5. “There are even 1 or 1.2%, but they must be combined with niacinamide or some anti-inflammatory ingredient such as a B group vitamin or hyaluronic acid that provides hydration and comfort.” In the case of alpha hydroxy acids, such as glycolic acid, the irritation and itching they produce to combat the passage of time sometimes happen at the time of application, unlike retinol. It is essential to consider the pH because the more acidic it is (between 3.5 and 4.2), the greater the penetration through the stratum corneum. The skin must be dehydrated to avoid producing more irritation than necessary. And for a star mix, the ideal is to combine these acids with hyaluronic acid to counteract possible irritation or dryness since it forms a film that retains water, which glycerin or sorbitol also do, according to Marta Hermosín.

Vitamin C that does not irritate

Regarding vitamin C, which illuminates, provides elasticity and fights stains, itching or stinging is not directly proportional to its effectiveness, as it sometimes depends on how it is formulated. As the pharmacist Aina Bordoy tells us, “the pure one (L-ascorbic acid) is usually formulated at a pH around 3.5, and therefore, at a higher concentration, it is more irritating on sensitive skin. It is a volatile molecule that oxidizes easily in contact with light, which is why it is often formulated encapsulated or in the form of derivatives associated with another molecule to ensure the stability of the active ingredient without having to lower its pH. : in this case, it is less irritating. As the expert says, “the skin’s reaction to an active ingredient depends partly on its resistance.”

Some sensitive skins redden easily and often do not tolerate certain products. They are hyper-reactive. On the other hand, others accept transforming active ingredients, such as retinoids or alpha hydroxy acids, at high concentrations without a problem. It is best to adapt the cosmetic routine to each skin type”, she advises. In the end, what happens to skin irritated by these ingredients is that they have an altered barrier function. Ceramides, cholesterol and fatty acids are the main components of the stratum corneum, the outermost layer of skin. They have anti-inflammatory properties, as they help maintain the integrity of this defence barrier. When these properties are diminished, it is necessary to counteract with soothing ingredients, such as allantoin, bisabolol, hyaluronic acid, and niacinamide.

And if we talk about cellulite…

In the case of some products that fight orange peel, the origin of the redness they can cause is different: it has to do with blood microcirculation. As explained by the Institute of Comprehensive Dermatology, active ingredients, such as menthol or camphor, stimulate it at the peripheral level with a change in temperature so that there is a blood appeal because oxygenated blood helps to detoxify. The product may sting slightly, but this is a temporary effect and is unrelated to its effectiveness.

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