What makes retinol effective?

Retinol's effectiveness is largely due to retinoids, according to WebMD. Retinoids prevent the breakdown of collagen, reduce visibility of wrinkles and lighten dark spots caused by aging or sun exposure.

Retinoids cause surface skin cells to die, prompting new cell growth underneath. They thicken the deeper layers of skin where wrinkles begin to form, according to WebMD.

Retinoids can be found in both over-the-counter retinol and stronger prescription versions, such as Retin-A and Trentinoin, indicates the Huffington Post. Retinol is photosensitive, and it should only be used at night. Anti-aging results may be noticed after one week of using retinol.