While prescription-strength retinoids may have an effect in a matter of weeks, it can take up to 6 months for OTC retinols to produce the same results. You may notice a difference in conditions like acne after 12 weeks, but sun damage and signs of aging can take much, much longer to improve.

How do you know if retinol is working?

Generally, it takes a few weeks to see results, but some OTC options may require months of regular use. Most dermatologists said you'll need to use retinol for a few weeks before you see results, but you should see improvements by 12 weeks with most products.

How long does it take for skin to adjust to retinol?

"Clinically, we've seen that it takes about three weeks for skin cells to adapt to retinoic acid and begin building their tolerance," says Engelman, which is why some degree of irritation is totally normal early on.