A powerful ingredient
The retinol you apply is first converted by the skin into retinoic acid, the active form of vitamin A. This makes retinol a gentler yet still effective form. Because it is such a potent ingredient, you may notice some side effects in the early stages, such as dryness, flaking or redness. For that reason, introduce it gradually and begin with once or twice a week.
Retinol is sensitive to sunlight
Retinol loses its effectiveness when exposed to sunlight, which is why it is often packaged in dark bottles. It is most often used as a night treatment, though you will also find it in eye creams, serums and day creams. If you use retinol during the day, always wear it beneath an SPF (or choose a day cream with SPF) to avoid irritation.
How much do you need?
The average concentration of retinol in a product is 0.3%. See how your skin responds to this level, then build up the percentage as it grows more tolerant. If you want to see more results, or to address a persistent skin concern such as acne within a certain time, you can add a higher percentage, up to around 1%, to your skincare routine.