As one of the most potent antioxidants, vitamin C protects the skin against free radical damage—the one that leads to early aging signs and dark spots. However, as good as it is, vitamin C has some downsides, and pronity to oxidation is one of them. Also, the active form of vitamin C is water-soluble, meaning it has molecules that are not small enough to penetrate the skin for intense effects. For this reason, several forms of vitamin C with different levels of solubility and stability are used in skincare products. Next, we take a closer look at the different forms of vitamin C and help you decide which one is best for your skin.
L-Ascorbic Acid
- Solubility: Water-soluble
- Strongest point: Purity and strength
- pH: 3.4
- Work best for: oily, mature, and combination skin
- Best at a concentration of: 5% to 20%
L-ascorbic acid is the gold standard when it comes to vitamin C in skincare products. It’s the pure stuff, the biologically active form of vitamin C—the most potent one because your skin doesn’t have to convert it. Virtually all other forms of vitamin C must first be converted to L-ascorbic acid in order to work on the skin. If you’re new to using vitamin C, take it slow with L-ascorbic acid to let your skin adjust to its strength.
Now, even though it’s the most active form, L-ascorbic acid has a couple of quirks. It’s water-soluble, meaning it’s not that well absorbed by the skin and mostly sticks to the surface. Also, L-ascorbic acid doesn’t like light or air much because they make it break down faster. That’s why you’ll often find it in special packaging or in products with a low pH level (acidic), which makes it stay stable and more effective.[1] However, if you have sensitive or dry skin, this low pH could be too much and cause sensitivities.
To give L-ascorbic acid a little more staying power, you can use it along with other antioxidants like vitamin E and ferulic acid, which increase the stability and antioxidant properties of L-ascorbic acid.
Good to know
- Applying L-ascorbic acid beneath sunscreen can double the photoprotection. Moreover, using a concentration higher than 20% doesn’t necessarily provide more benefits and can instead lead to irritation.[1] Studies have found that a serum with 10% vitamin C can diminish UVB-induced skin damage by 52% and reduce sunburn cell formation by 40-60%.[2]
- Opt for vitamin C products packaged in amber, air-tight glass bottles, which protect the ingredient from oxidation due to air and light exposure.
Products
Sodium Ascorbyl Phosphate
- Solubility: Water-soluble
- pH: 7
- Work best for: acne-prone, oily, and normal skin
- Strongest point: Antimicrobial
- Best at a concentration of: 5% to 10%
Sodium ascorbyl phosphate (SAP) is a stable, water-soluble form of vitamin C with a salt molecule attached. It’s more skin-friendly than L-ascorbic acid, especially for those with sensitive skin, because it’s effective at a neutral pH level and doesn’t irritate. According to studies, it works best in concentrations of 0.1% to 3%, and it’s more easily absorbed by the skin.[3]
Those battling acne might find a friend in SAP. Studies, including one from the International Journal of Cosmetic Science, show that even at a modest 1% concentration, SAP can fend off acne-causing bacteria. At 5%, it might work even better than common treatments like benzoyl peroxide.[4]
Good to know
- Sodium ascorbyl phosphate works better when combined with ascorbyl palmitate, another stable form of vitamin C.[5]
Products
Magnesium Ascorbyl Phosphate
- Solubility: Water-soluble
- pH: 7
- Work best for: acne-prone, sensitive, and dry skin
- Best at a concentration of: 5% to 10%
- Strongest point: Hydrating
Magnesium ascorbyl phosphate (MAP) is a stable form of vitamin C that works at neutral pH. It’s more suitable for dry and sensitive skin than other forms since it’s less irritating. Unlike L-ascorbic acid, MAP doesn’t degrade in water-based formulas and it’s actually added to products to stabilize them.[6]
Magnesium ascorbyl phosphate is a potent free radical scavenger, skin hydrator, and brightener. Moreover, it’s been found that MAP works well to reduce inflammatory acne.[7] Magnesium ascorbyl phosphate is considered a stable and effective antioxidant for the skin and usually comes in concentrations of around 5%. Its neutral pH makes it easy to formulate into various products and reduces the chances of sensitivity.
Good to know
- Products with 2% glutathione, 1% vitamin E, and 3% magnesium ascorbyl phosphate have higher brightening effects than 4% hydroquinone cream.[8]
Products
Ascorbyl Palmitate
- Solubility: Oil-soluble
- pH: <6
- Works best for: sensitive, dry, and mature skin
- Strongest point: Tolerability
- Best at a concentration of: 0.1 to 1%
Ascorbyl palmitate is an oil-soluble form of vitamin C with an added fatty acid (palmitic acid) to make it more stable and gentler.[9] Since ascorbyl palmitate is combined with a fatty acid, it’s more hydrating than other forms of vitamin C and more suitable for dry and sensitive skin.
However, even if it’s soluble in oil and penetrates the skin better than L-ascorbic acid, its conversion into the pure form of vitamin C is limited.[10] This means it might be less effective than forms out there.
3-O-ethyl-ascorbic acid
- Solubility: Oil- and water-soluble
- pH: Between 4 and 6
- Works best for: sensitive, dry, and mature skin
- Best at a concentration of: 0.1 to 1%
3-O-ethyl-ascorbic acid is a stable derivative of L-ascorbic acid. Since it’s soluble in both oil and water, this form of vitamin C can easily penetrate the skin. It carries antioxidant, anti-inflammatory, and collagen-boosting properties, and it’s especially good at brightening the skin.[11]
Ascorbyl Glucoside
- Solubility: Water-soluble
- pH: Between 4 and 6
- Works best for: oily, acne-prone, dry, and combination skin
- Best at a concentration of: 0.1 to 1%
- Strongest point: It’s gentle
Ascorbyl glucoside is a stabilized derivative of vitamin C that contains glucose (sugar) molecules. It’s gentler on the skin than other forms.
Tetrahexyldecyl Ascorbate
- Solubility: Oil-soluble
- pH: Lower than 6.5
- Works best for: oily, acne-prone, dry, and normal skin
- Best at a concentration of: 0.1 to 1%
Tetrahexyldecyl ascorbate (THD) is often used in skincare due to its ability to penetrate the epidermis. Its benefits are similar to the purest form of vitamin C; it shields against oxidative stress, enhances collagen production, brightens, heals, and increases hydration. For anti-aging benefits, THD should be paired with retinol, vitamin E, and CoQ10.[10]
What’s the best form of vitamin C
L-ascorbic acid is the best form of vitamin C in terms of potency, while magnesium ascorbyl phosphate is the most stable form used in skincare products. Also, ascorbyl glucoside and ascorbyl palmitate are the gentlest forms of vitamin C that work great for people with sensitive skin.
- Can vitamin C be absorbed through the skin?
Vitamin C can be absorbed through the skin. It can provide antioxidant protection and boost collagen production at the right concentration and pH level.
- Is oxidized vitamin C bad for the skin?
Oxidized vitamin C, often seen as a yellowish discoloration, can be less effective. While not harmful to the skin, it’s not as beneficial as non-oxidized vitamin C.
Women’s Concepts uses reliable sources, including dermatologists’ insights, clinical trials, and scientific journals, to find accurate information and support all the facts shared in our articles. All statements and claims have clear and legit references. Read our editorial policy to learn more about our sources of information, our process of researching and fact-checking the content, and how our team strives to keep all articles updated, completed, and trustworthy.
- Al-Niaimi F, Chiang NYZ. Topical Vitamin C and the Skin: Mechanisms of Action and Clinical Applications. J Clin Aesthet Dermatol. 2017 Jul;10(7):14-17. Epub 2017 Jul 1. PMID: 29104718; PMCID: PMC5605218.
- Telang PS. Vitamin C in dermatology. Indian Dermatol Online J. 2013 Apr;4(2):143-6. doi: 10.4103/2229-5178.110593. PMID: 23741676; PMCID: PMC3673383.
- International Journal of Toxicology, 24(Suppl. 2):51–111, 2005, Final Report of the Safety Assessment of L-Ascorbic Acid, Calcium Ascorbate, Magnesium Ascorbate, Magnesium Ascorbyl Phosphate, Sodium Ascorbate, and Sodium Ascorbyl Phosphate as Used in Cosmetics
- Klock J, Ikeno H, Ohmori K, Nishikawa T, Vollhardt J, Schehlmann V. Sodium ascorbyl phosphate shows in vitro and in vivo efficacy in the prevention and treatment of acne vulgaris. Int J Cosmet Sci. 2005 Jun;27(3):171-6. doi: 10.1111/j.1467-2494.2005.00263.x. PMID: 18492184.
- Hira Khan, Naheed Akhtar, Atif Ali, Fortification of facial skin collagen efficacy by combined ascorbyl palmitate and sodium ascorbyl phosphate, January 2018,
- Slim Smaoui, Hajer Ben Halima, and Adel Kadri, Application of l-Ascorbic Acid and its Derivatives (Sodium Ascorbyl Phosphate and Magnesium Ascorbyl Phosphate) in Topical Cosmetic Formulations: Stability Studies, Department of Life Sciences, Sciences Faculty of Sfax, BP 1171, Sfax 3000, Tunisia
- Lee WJ, Kim SL, Choe YS, Jang YH, Lee SJ, Kim DW. Magnesium Ascorbyl Phosphate Regulates the Expression of Inflammatory Biomarkers in Cultured Sebocytes. Ann Dermatol. 2015 Aug;27(4):376-82. doi: 10.5021/ad.2015.27.4.376. Epub 2015 Jul 29. PMID: 26273151; PMCID: PMC4530145.
- Andy Manggabarani, Farida Tabri, Anis Irawan, Arifin Seweng, Agussalim Bukhari, Khairuddin Djawad, A randomized study, Effectivness of glutathione (gsh) 2%, tocopheryl acetate 1%, and magnesium ascorbyl phosphate 3% combination cream compared with hydroquinone 4% cream as a skin lightening agent
- Teeranachaideekul V, Müller RH, Junyaprasert VB. Encapsulation of ascorbyl palmitate in nanostructured lipid carriers (NLC)–effects of formulation parameters on physicochemical stability. Int J Pharm. 2007 Aug 1;340(1-2):198-206. doi: 10.1016/j.ijpharm.2007.03.022. Epub 2007 Mar 24. PMID: 17482778.
- Safety Assessment of Ethers and Esters of Ascorbic Acid as Used in Cosmetics
- Liao WC, Huang YT, Lu LP, Huang WY. Antioxidant Ability and Stability Studies of 3-O-Ethyl Ascorbic Acid, a Cosmetic Tyrosinase Inhibitor. J Cosmet Sci. 2018 Jul/Aug;69(4):233-243. PMID: 30311899.
