Glycolic acid is a chemical exfoliant derived from sugarcane that is used in many skin care products:

How it works
Glycolic acid is an alpha hydroxy acid (AHA) that removes dead skin cells and oils, which can improve the appearance of skin texture, tone, and radiance. It can also help with collagen production and support skin moisture.

Uses
Glycolic acid is used to treat acne, hyperpigmentation, dark spots, stretch marks, and other signs of aging.

How to use
Glycolic acid is available in cleansers, serums, toners, and creams. You should start slowly when introducing glycolic acid to your routine, and increase the frequency as your skin adjusts.

Side effects
Using glycolic acid too frequently, at too high a concentration, or incorrectly can cause skin irritation or damage. It can also increase your skin’s sensitivity to the sun, so you should use sunscreen and limit sun exposure while using it.

Precautions
You should avoid using glycolic acid if you have dry skin, sensitivity, or cystic acne. If you have rosacea or painful cystic acne, you should consult a dermatologist.