Free radicals are molecules produced during normal metabolism and by outside exposures such as sunlight and pollution; they can damage skin cells. Vitamin C can help neutralize them. It also supports collagen synthesis, which means making collagen, the protein that gives skin structure and support. Your body makes less collagen with age, which contributes to fine lines and wrinkles.13

Results take time. One study found that daily use for three months improved fine and coarse wrinkles on the face and neck, as well as overall skin texture and appearance. Clinical trials have also reported improvement in dark spots, but more research is needed to confirm the brightening effect. With regular long term use, topical vitamin C may also reduce dryness, fine wrinkles and uneven pigmentation. Those results are not a promise for every serum: the active ingredient, formula and stability all affect how well a product works.245

How to choose a vitamin C product

Vitamin C comes in serums and other skin care products. Labels may list it as ascorbic acid or L ascorbic acid. Clinical trials have studied products with an active form of vitamin C at 10% to 20% strength and a pH below 3.5, a measure of acidity. Formulas vary in stability and absorption, and some products do not deliver much vitamin C into the skin. An opaque container helps limit light exposure, which can inactivate vitamin C. A clear bottle gives light a front row seat, which is a poor arrangement for an ingredient light can inactivate.134

How to use vitamin C serum

  1. 1In the morning, wash your face with a gentle cleanser.
  2. 2Apply a few drops of serum to your face and neck.
  3. 3Apply moisturizer, then broad spectrum sunscreen. Vitamin C adds to sun protection when paired with sunscreen, but it does not replace sunscreen or sun protective clothing.
  4. 4If your skin tolerates it, use the serum daily. If you are new to it, start every other day and increase to daily use.
4

Apply serum after cleansing and before moisturizer. A serum is not a moisturizer, and its place in the routine is not a substitute for sunscreen. If you already use a product containing vitamin C, check the ingredients before adding another one; doubling up is not required for the ingredient to count.2

A visible change can take up to three months of consistent use, which is a long time to share a bathroom shelf with an ingredient that has not finished introducing itself. Keep sunscreen in the routine while using vitamin C, since vitamin C does not replace sun protection.4

Who should be careful

Sensitive skin can react to concentrated ingredients. A small patch test is a sensible first step if you have sensitive skin or a known allergy to an ingredient. Mild tingling can happen, and initial stinging or redness often eases with continued use. Stop using the product and consult a physician if you have substantial discomfort or irritation. Vitamin C products have been studied in adults and are not recommended for children.246

Use caution when combining an acidic vitamin C serum with retinol products. Combining a vitamin C serum with a retinol cream can irritate skin, and extra care is warranted if a prescription retinol is also part of your routine. If you have oily or acne prone skin, consider a vitamin C formula designed to address oil or one that includes an ingredient such as salicylic acid.24

Does vitamin C from food help skin too?

Vitamin C in food supports collagen formation and works as an antioxidant. Citrus fruits and red or green peppers are food sources. For healthy adults, meeting nutrient needs through food is preferred; supplements can be useful when a doctor identifies a deficiency or another reason for extra nutrients. A topical serum and dietary vitamin C are different ways of using the same nutrient, not interchangeable products.7

Why did my vitamin C serum turn orange?

Vitamin C is unstable when exposed to oxygen, and light can inactivate it. Because formulas differ in strength and stability, an orange color alone cannot give a precise measure of how much active vitamin C remains. Check how long the product has been open: vitamin C products can start to lose effectiveness after about six months. If yours is around that age, replacing it is reasonable.134

Where this answer comes from

  1. 1Anti-Aging Skin Care: Ingredients and Routinehealth.clevelandclinic.org
  2. 2Skin serum: What it can and can’t dohealth.harvard.edu
  3. 3Vitamin C creamdermnetnz.org
  4. 4Why is topical vitamin C important for skin health?health.harvard.edu
  5. 5Skin ageingdermnetnz.org
  6. 6Popular Skin Care Ingredients Explainedhealth.clevelandclinic.org
  7. 7Should I take vitamins or supplements for my skin?aad.org