Can I use vitamin C and AHA together?

Why separating them is a sensible start

AHAs exfoliate the surface of the skin by loosening the connections between surface cells. Layering vitamin C serum with chemical exfoliants such as AHAs can affect skin pH, and using too many active products makes dryness and irritation more likely. The practical distinction is between keeping both products in your routine and applying both at once. Keeping the product lineup short makes a routine easier to read, which is more than many bathroom shelves can say for themselves.23

What matters about the AHA

AHA is a group of acids, not one single formula. Glycolic and lactic acids are common in skin care, and glycolic acid can penetrate skin more deeply than other AHAs. AHAs help shed old surface cells, which can improve the look of fine lines, brown marks and dry spots with regular use. The amount of exfoliation a product delivers depends on its AHA type, concentration, pH and other ingredients.124

For glycolic or lactic acid, a consumer safety panel considered products safe for consumer use at 10 percent or less, with a pH of 3.5 or higher, and with sun protection built into the formula or stated in the directions. Products from medical practitioners can be stronger than those sold through pharmacies.14

A professional glycolic peel is not the same as a leave on product. Peel strengths range from 20 to 70 percent, depending on skin sensitivity; the solution is applied briefly and then washed off. Treated skin can be pink immediately afterwards, and some peeling can happen over the next few days.1

How to use both in a routine

1. 1Start with one new product at a time and test a small amount on one area of skin. When you are starting glycolic acid, avoid using it in the same application as vitamin C, other exfoliants such as lactic or salicylic acid, or retinol.
2. 2In the morning, cleanse and apply vitamin C serum after cleansing. Use moisturizer after the serum, then sunscreen as the final step. Use one serum at a time.
3. 3Use a leave on AHA at night. For glycolic acid, start once or twice a week and gradually increase only if your skin tolerates it. Follow the product directions, since AHA products differ in strength and formula.
4. 4If you want both products in your routine, keep vitamin C in the morning and AHA in the evening. You can also use them on alternate days rather than in the same application.

Serum is an optional step in a basic routine, an unusually modest job description for a product category.3

Protect your skin from the sun

AHAs can increase skin sensitivity to ultraviolet light while you use them and for up to a week after stopping. Use sunscreen, protective clothing and limited sun exposure during use and for the following week. With glycolic acid, use broad spectrum sunscreen with SPF 30 or higher during the day and reapply it every two hours. Vitamin C serum can reinforce sunscreen, but it does not replace it.2345

What results are realistic?

Regular AHA use can improve the appearance of fine lines, brown marks and dry spots by encouraging surface cells to shed. With high concentrations and long term use, AHAs can also affect deeper skin layers, where collagen and elastin regenerate and fine lines can become less obvious. Over the counter glycolic acid can take several months of consistent use before brightness or pigmentation changes are noticeable. Professional peels can produce more dramatic differences, but they are a separate treatment with different strengths and directions.12

Topical vitamin C can protect against photoaging when it is made in a stable formulation. Many preparations are not well absorbed, and many product claims lack rigorous testing, so a serum name alone does not tell you how much benefit to expect. There is no single reliable timeline for every vitamin C serum because formulation quality varies.6

Who should be careful?

Be cautious with glycolic acid if you have sensitive or dry skin, rosacea, eczema, an active skin infection, or skin that is not healing. Start slowly and do not add several active products at once. AHA treatments are considered safe in pregnancy, and low concentration glycolic acid is generally considered safe, but pregnant or breastfeeding people should check with a healthcare provider before using glycolic acid.12

When to stop

Stop using a product if you develop signs of contact dermatitis or skin irritation, and make an appointment with a dermatologist.3