What percentage of retinol should be applied?

Widely used in the skincare industry, retinol is a form of fat-soluble vitamin A, meaning it is soluble in lipids, the molecules that make up the intercellular cement of the corneal layer. If retinol is so well-regarded, it's because it is very versatile and offers numerous benefits to the skin. It indeed has antioxidant, exfoliating, depigmenting, and firming properties. Retinol is particularly appreciated for the latter, which comes notably from its ability to accelerate cell renewal and to stimulate the dermal synthesis by fibroblasts of three matrix molecules that contribute to maintaining the skin's structure: collagen, elastin, and glycosaminoglycans (hyaluronic acid). Used regularly, retinol restores firmness, flexibility, and density to the face and reduces the appearance of wrinkles.

However, retinol is associated with a potential for irritation, resulting in redness and flaking in individuals with sensitive skin. This is why its use in non-rinse cosmetic products is limited to 0.3% by European Regulation No 1223/2009.

If this is your first time using a retinol treatment, it is advisable to opt for a product with a low dosage, that is, a concentration of about 0.01-0.05%. This will allow you to test if your skin tolerates this active ingredient well. This recommendation also applies to individuals with dry or sensitive skin. It is also recommended to apply a retinol treatment every third evening during the initial weeks, then gradually increase to once a week. This usage pattern allows the skin time to adapt to this active ingredient and minimises the risk of irritation.

This low concentration of retinol is optimal for slowing the appearance of age-related signs while maintaining your skin's balance. According to a Chinese study, low concentration retinol, ranging between 1500 and 2500 IU, has significant effects on skin brightness, elasticity, and uniformity. This research was conducted with 72 Korean women aged between 40 and 59 who used retinol for 24 weeks.

A gradual introduction of retinol, even at a low concentration, allows for visible benefits on the skin while minimising the risk of irritations associated with this active ingredient.

If you have an uneven complexion or if your skin lacks firmness, it is recommended to opt for a retinol concentration between 0.05 and 0.1%. This intermediate dosage offers a good balance between effectiveness and tolerance, allowing it to address the initial signs of ageing without harming the skin. Regular use, at a rate of two to three evenings per week, can yield satisfactory results. However, check your skin's tolerance to the treatment to adjust the frequency of use. If signs of irritation appear, such as redness or feelings of tightness, it is advisable to space out the applications and enhance the skin's hydration.

Unlike low-dose retinol treatments, those with a medium concentration ensure quicker visible results, typically within about 8 weeks. This dosage of retinol effectively stimulates cell renewal and collagen production, thus improving the texture and elasticity of the skin. In addition to early skin ageing, these medium-dose cream and serum formulas also help combat the effects of environmental pollution and skin thinning.

For pronounced uneven skin tone or deep wrinkles, it is recommended to use a high-dosage retinol treatment. This could be a cream, a serum, or another 0.1 to 0.3% formula that you will use according to the manufacturer's instructions. This high concentration of retinol also acts on the prevention of comedone formation in acne-prone skin, as well as on cell renewal. Indeed, in addition to skin sagging, retinol acts on imperfections thanks to its comedolytic action. This molecule works by increasing the regeneration of skin cells and accelerating the elimination of corneocytes, which promotes an aerobic environment inhospitable for Cutibacterium acnes, the main bacteria involved in acne.

Recent research studies have compared the efficacy of 0.3% and 0.5% serums. For this purpose, 37 volunteers were recruited. Over a period of 12 weeks, they applied one of the serums to one side of their face and the other serum to the other side. At the end of the study, a significant improvement in skin tone uniformity and elasticity was observed on both sides of the face. No significant difference was noted between the two serums. However, a significantly higher number of side effects were associated with the 0.5% retinol, particularly irritations and itching, whereas the 0.3% retinol was well tolerated.

The regulatory threshold in Europe of 0.3% thus represents a good balance between efficacy and tolerance.

• Règlement (CE) No 1223/2009 du Parlement Européen et du Conseil.

• ROEDER A. & al. Retinoids in the treatment of skin aging: an overview of clinical efficacy and safety. Clinical Interventions in Aging (2006).

• ODDOS T. & al. Antiaging Action of Retinol: From Molecular to Clinical. Skin Pharmacology and Physiology (2009).

• BUDZISZ E. & al. Randomized parallel control trial checking the efficacy and impact of two concentrations of retinol in the original formula on the aging skin condition: Pilot study. Journal of Cosmetic Dermatology (2019).

• ERKIERT-POLGUJ A. & al. A Clinical Anti-Ageing Comparative Study of 0.3 and 0.5% Retinol Serums: A Clinically Controlled Trial. Skin Pharmacology and Physiology (2020).

• KIM E. & al. A long term study of the difference in efficacy and effect rate of various concentrations of retinol (1500-6600 IU) in middle aged women. Archives of Dermatological Research (2023).