Vitamin C for dark spots: what the evidence shows

Vitamin C is one of the most popular skin care ingredients for dark spots. It is also one of the five ingredients the American Academy of Dermatology (AAD) lists as able to fade them. This guide looks at how vitamin C works on pigment, what the trials show, why it is hard to keep stable, and how to use it. It is part of Skinli's guide to hyperpigmentation.

How vitamin C works on dark spots

Skin makes melanin, the pigment behind dark spots, with the help of an enzyme called tyrosinase. A 2013 review in the Indian Dermatology Online Journal explains that vitamin C binds to copper at the working site of this enzyme and blocks it, so less melanin forms.

The review places vitamin C among ingredients that interrupt the steps of making pigment. In other words, vitamin C slows the making of pigment and leaves the pigment cells themselves unharmed.

The same review says vitamin C has anti-inflammatory activity, and that it can support wound healing and help prevent the dark marks that follow inflammation. The review gives this as a property of the ingredient. It does not cite a trial in acne marks for it.

What the evidence shows

Most research on vitamin C and pigment is on melasma, the brown patches often linked to hormones. A 2010 review in the Journal of Clinical and Aesthetic Dermatology says vitamin C and its related forms have been shown to be safe with some effect in Latino and Asian patients, but that most studies involved melasma and did not include marks left after inflammation.

One trial compared vitamin C with hydroquinone, a stronger prescription lightener:

Detail	2004 trial, International Journal of Dermatology
Who	16 women with melasma
Design	Double-blind, randomized. 5% vitamin C cream on one side of the face, 4% hydroquinone cream on the other
How	Applied at night for 16 weeks, with sunscreen every day
Patients' own rating	93% good or excellent on the hydroquinone side, 62.5% on the vitamin C side
Skin color measurement	No statistical difference between the two sides
Side effects	68.7% on the hydroquinone side, 6.2% on the vitamin C side

The authors concluded that hydroquinone worked better, but that vitamin C may still have a role because it causes almost no side effects. It can be used alone or with other treatments.

Hydroquinone is not a home option in the US today. The FDA says no skin lightening product is legally sold over the counter, and the AAD says hydroquinone is no longer available without a prescription.

Vitamin C for acne marks

For the flat marks that acne leaves, vitamin C has less direct evidence than azelaic acid or retinoids. It is still on the AAD's list of ingredients that can fade dark spots. The main difference is that vitamin C does not treat acne, while azelaic acid and retinoids do. With active acne, one of those two covers both problems, and the azelaic acid and retinol and tretinoin pages explain them.

Vitamin C can suit people who find retinoids too irritating, since the 2004 trial found side effects in 6.2% of vitamin C sides. On darker skin, low irritation matters, because the AAD says irritation itself can darken spots.

The stability problem

Vitamin C is hard to keep stable. The 2013 review says L-ascorbic acid, the pure form, breaks down on exposure to light and turns into a compound that gives the product a yellow color. The 2010 review says early vitamin C products were unstable, which led chemists to create more stable related forms.

The 2013 review gives these details:

• pH. L-ascorbic acid stays stable and passes into the skin best at a pH below 3.5, which is acidic.
• Strength. The effect of a vitamin C serum rises with concentration, but only up to 20%.
• Stable forms. Magnesium ascorbyl phosphate is the most stable and preferred of the related forms. Ascorbyl palmitate is another.

The 2010 review says vitamin C is typically used at 5% to 10%. The 2013 review says the yellow color comes from vitamin C breaking down, so a product that has turned yellow has changed from its original form.

How to use vitamin C

1. Start with sunscreen. The AAD says effective treatment for dark spots begins with sunscreen, and recommends a tinted one with iron oxide, SPF 30 or higher.
2. Patch test first. Try it on a small area for several days. The guide on how to patch test a new skincare product gives the steps.
3. Follow the label. Strengths and forms differ, so the product's own directions come first. In the 2004 trial, the cream went on at night.
4. Store it away from light. Keep the cap closed and the bottle out of the sun.
5. Add one new product at a time, so you know what caused any reaction.

Side effects

Vitamin C is one of the gentler options. The 2013 review lists minor side effects: a yellowish tint on the skin, lighter hair and stained clothes, all caused by the vitamin C breaking down. It says stinging, redness and dryness happen rarely. The AAD's rule applies: if a product burns or stings when you put it on, stop using it.

Vitamin C and sunscreen

Vitamin C is often called a sun protector, and the review explains the limit of that claim. Vitamin C protects by neutralizing harmful molecules that sunlight creates in the skin, and it absorbs no ultraviolet light. The review says sunscreen works best when combined with a topical antioxidant such as vitamin C.

So vitamin C can add to sunscreen, but it cannot replace it. For dark spots, the order is sunscreen first, then any fading ingredient.

Vitamin C for melasma

The AAD names vitamin C as one of the gentler medicines a dermatologist may use for melasma, along with azelaic acid and kojic acid. It also says that if you use a non-prescription melasma product, you should use it for no longer than three to six months, and see a dermatologist if it has not helped by then. Read the melasma page for the full plan.

How long to try it

The 2004 trial ran for 16 weeks, with checks each month. That is a sensible minimum for judging any fading ingredient. For melasma, the AAD sets an upper limit of three to six months for a non-prescription product. For acne marks, the AAD says a mark a few shades darker than your skin usually fades within 6 to 12 months once the acne stops, with or without a cream. A monthly photo in the same light is the best way to see the change.

Does eating vitamin C help?

Many people ask whether oranges or vitamin C pills fade dark spots. The 2013 review says the body cannot make vitamin C, so it comes from foods such as citrus fruits, green leafy vegetables, strawberries, papaya and broccoli. It also says the gut absorbs only a limited amount, even when people take high doses by mouth, and that the level reached in the skin is too low when vitamin C is taken orally. For dark spots, the studies above used vitamin C applied to the skin.

Vitamin C compared with the other options

Ingredient	Main evidence for dark spots	Also treats acne?	Main caution
Vitamin C	Small melasma trials	No	Breaks down in light
Azelaic acid	Trials in acne marks and melasma	Yes	Rare light patches
Retinoids	Trials in acne marks, sun spots and melasma	Yes	Irritation
Niacinamide	Trials in melasma and sun-related spots	Not on the AAD list	Not studied for acne marks on darker skin

Glycolic acid and kojic acid are also on the AAD list. The niacinamide page covers the ingredient many people use alongside vitamin C.

Check the spot first

Before treating a spot on your own, make sure it is the kind that creams can fade. The AAD recommends a skin exam before treating age spots, because what looks like an age spot could be skin cancer. Any spot that is new and unlike your other spots, or that changes, itches or bleeds, needs a dermatologist. Read when a dark spot needs a doctor for the signs.

Setting expectations

Vitamin C is a gentle choice for uneven tone and dark spots, with modest evidence and few side effects in the trial above. It works slowly and works best alongside daily sunscreen. For how long different spots take to fade, read how long dark marks take to fade.