Diminishing the appearance of wrinkles, smoothing out imperfections, restoring radiance to the complexion, and reducing signs of hyperpigmentation... retinol is considered one of the key active ingredients in skincare with scientifically proven effects. However, to fully reap its benefits, certain rules must be followed for its proper use. For instance, it cannot be applied at just any time of the day. It is often reported that retinol should be used in the evening, even though some retinol products have been designed for daytime use. But what are the reasons for this?
Why should retinol be used in the evening?
- Reason #1: Retinol is what's known as a "photosensitizing" agent
- Reason #2: The sun breaks down retinol
- Reason #3: At night, the skin regenerates more quickly
Reason #1: Retinol is what's known as a "photosensitizing" agent.
Although the results are mixed, retinoids are believed to be photosensitizing agents. They would make the skin slightly sensitive to UV radiation. Photosensitivity involves potentially causing a skin reaction following exposure to the sun, or being more susceptible to sun damage such as sunburn. As a precaution, it is recommended to cleanse the skin the next morning to remove unabsorbed retinol molecules from the epidermis and apply a broad-spectrum sun protection.
Reason #2: The sun breaks down retinol.
Direct sunlight has the ability to degrade retinol, which can compromise its effectiveness. When exposed to UV light, retinol absorbs light energy in the UVA and UVB range (315 - 400 nm), leading to a redistribution of charges and alterations in molecular bonds. This stimulation of retinol, or its derivatives, by UV rays generates various reactive oxygen species, including singlet oxygen and the superoxide radical. These byproducts can have a pro-oxidant effect and damage various cellular components, such as lipids, DNA, and proteins. Therefore, it is preferable to use products containing retinol in the evening.
Reason #3: At night, the skin regenerates more quickly.
At night, all the conditions are met to trigger skin renewal and further activate blood circulation. During this time, skin cells multiply three times more than during the day. This ensures proper skin repair to best face the day and protect it from external aggressions. It is also during these hours that the skin is more permeable and therefore more receptive to treatments. Additionally, around the age of thirty, cellular renewal slows down and the epidermis thins. Thus, the evening is the ideal time to provide the skin with powerful actives like retinol to restart the process of cellular regeneration.
FU P. P. & al. Photodecomposition and phototoxicity of natural retinoids. International Journal of Environmental Research and Public Health (2005).
HOWARD P. C. & al. Photoreaction, phototoxicity, and photocarcinogenicity of retinoids. Journal of Environmental Science and Health, Part C: Environmental Carcinogenesis and Ecotoxicology Reviews (2013).