Produto Skincare · Blog

Vitamin C: what it does and how to use it

By the Produto Skincare team · Updated on November 4, 2026

Published on November 2, 2026 · 5-minute read

Vitamin C serum bottle next to sliced oranges, on light marble in sunlight

Vitamin C is one of the most popular skincare ingredients. It is an antioxidant, plays a part in collagen production and may help with dark spots (Badash et al., 2026). Clinical studies are still limited (Al-Niaimi et al., 2017), and using it the wrong way can waste the product (or even irritate your skin).

Summary: Use it preferably in the morning, before sunscreen. Start with 10%. Store it somewhere dark and cool.

What vitamin C does

Brightens the tone: helps make skin tone more even (Badash et al., 2026)
Helps with dark spots: reduces melanin formation (Al-Niaimi et al., 2017). In melasma, a trial with 5% vitamin C lightened less than hydroquinone, but with almost no side effects (Espinal-Perez et al., 2004)
Antioxidant: helps protect the skin from environmental damage, especially from the sun (Badash et al., 2026)
Complements sunscreen: it works through a different pathway from UV filters, but does not replace SPF (Murray et al., 2008)
Supports collagen: increases production and reduces breakdown, which may soften fine lines (Al-Niaimi et al., 2017)

When to use it: preferably in the morning

Most people use it in the morning, because it:

Protects against the day's free radicals
Adds to the protection of sunscreen (Murray et al., 2008)

But using it at night is not a waste. In a study on pig skin, vitamin C stayed in the skin for days after application (Pinnell et al., 2001), and a melasma trial used the product at night (Espinal-Perez et al., 2004).

Ideal concentration

Concentration	For whom	What we know
5-10%	Beginners, sensitive skin	Milder. In the 5% trial, there were almost no side effects (Espinal-Perez et al., 2004)
10-15%	Most people	A common range. A study in people used 15%, together with vitamin E and ferulic acid (Murray et al., 2008)
15-20%	Experienced users	In pig skin, 20% was the concentration with the best absorption (Pinnell et al., 2001)
Above 20%	—	In the same study, it did not increase absorption

How to use it (step by step)

Cleanse your face
Apply vitamin C to dry skin (3-5 drops)
Wait 1-2 minutes for it to absorb
Apply moisturizer
Finish with sunscreen (a must!)

Combinations that work

Combination	Result
Vitamin C + sunscreen	✅ Each complements the other (Murray et al., 2008)
Vitamin C + vitamin E	✅ They work together against oxidation (Al-Niaimi et al., 2017)
Vitamin C + ferulic acid	✅ A more stable formula; with vitamin E, it protected the skin against UV damage in a study in people (Murray et al., 2008)
Vitamin C + niacinamide	⚠️ Studies on the pair are lacking; if it stings, use them at different times of day
Vitamin C + retinol	⚠️ Together they may irritate more; the simplest approach is vitamin C in the morning and retinol at night

Sources

Badash A, et al. Vitamins and the skin: Vitamin C in dermatology. Clin Dermatol, 2026. PubMed 41690651 · DOI
Al-Niaimi F, et al. Topical Vitamin C and the Skin: Mechanisms of Action and Clinical Applications. J Clin Aesthet Dermatol, 2017. PubMed 29104718
Espinal-Perez LE, et al. A double-blind randomized trial of 5% ascorbic acid vs. 4% hydroquinone in melasma. Int J Dermatol, 2004. PubMed 15304189 · DOI
Murray JC, et al. A topical antioxidant solution containing vitamins C and E stabilized by ferulic acid provides protection for human skin against damage caused by ultraviolet irradiation. J Am Acad Dermatol, 2008. PubMed 18603326 · DOI
Pinnell SR, et al. Topical L-ascorbic acid: percutaneous absorption studies. Dermatol Surg, 2001. PubMed 11207686 · DOI

References checked on PubMed in November 2026. Claims about effectiveness are based on the abstracts of these studies.