Vitamin C is the loyal devotee you need in your routine, regardless of skin type or age. As one of the most potent antioxidants, vitamin C shields the skin against free radical damage — the one that leads to early aging signs. However, as good as it is, vitamin C has its downsides, and pronity to oxidation is one of them. Also, the active form of vitamin C is water-soluble, meaning its molecules are not small enough to penetrate the skin for intense results. For this reason, many more types of vitamin C keep popping up in skincare, with diverse solubility and stability levels. 

While that’s a good thing, it makes picking the best form of vitamin C for your skin a difficult mission. In this post, we break down everything you need to know about the main types of vitamin C in skincare, so you will always choose the one that serves you best. Using a form of vitamin C that is not suitable for your skin type or a concentration that’s too high without building tolerance at first might lead to irritation. So read on.

The types of vitamin C in skincare

Before we go to the good bit, you should know that all forms of vitamin C are converted in the body to L-ascorbic acid (the purest form of vitamin C), the form the body can use. This makes L-ascorbic acid the most potent form but also the most likely one to irritate. 

L-Ascorbic Acid  

• Solubility: water-soluble
• Strongest point: purity
• pH: 3.4
• Skin types: oily, mature, normal, combination
• Best at a concentration of: 5% to 20% 

L-ascorbic acid is the most biologically active form of vitamin C, meaning it is the strongest as it doesn’t require to be converted to deliver benefits. For this reason, if you’re a vitamin C starter and planning to begin with the pure form of vitamin C, it is wise to start slowly to help your skin adjust to it. 

As a water-soluble compound, L-ascorbic acid has poor skin penetration, meaning it acts more on the top layer of the skin. The less pleasant thing about L-ascorbic acid is its pronity to degradation when exposed to light and air. Due to its vulnerability, L-ascorbic acid should be formulated without water or at a pH below 3.4 to increase its stability and permeability.^[1] Remember that this might be too acidic for sensitized or dry skin. Another way to increase L-ascorbic acid’s stability is to use it along with other antioxidants, such as vitamin E and ferulic acid.

Sodium Ascorbyl Phosphate

• Solubility: water-soluble
• pH: 7
• Skin types: acne-prone, oily, combination
• Strongest point: antimicrobial
• Best at a concentration of: 5% to 10% 
• What else: more stable than magnesium ascorbyl phosphate

Sodium Ascorbyl Phosphate (SAP) is a water-soluble form of vitamin C with a salt molecule attached, making it easier to sink into the skin. Unlike L-ascorbic acid, SAP has excellent stability up to pH 7 and is gentler than L-ascorbic acid. Usually, sodium ascorbyl phosphate fulfills its antioxidant, collagen-inducing, and brightening benefits when used in concentrations ranging from 0.0% to 3%.^[3]

Furthermore, a review by the International Journal of Cosmetic Science found that 1% SAP has major antimicrobial effects on acne-causing bacteria, making it a go-to for acne sufferers. Also, 5% sodium ascorbyl phosphate proved to be more effective than benzoyl peroxide and salicylic acid in treating and preventing acne without side effects.^[4]

Magnesium Ascorbyl Phosphate

• Solubility: water-soluble
• pH: 7
• Skin types: acne-prone, sensitive, dry
• Best at a concentration of: 5% to 10% 
• Strongest point: hydrating
• What else: more stable than magnesium ascorbyl phosphate

Magnesium ascorbyl phosphate (MAP) is a stable form of vitamin C in skincare, which works great when formulated at neutral pH. For this reason, magnesium ascorbyl phosphate is suitable for dry and sensitive skin, as it’s less irritating. Unlike L-ascorbic acid, MAP doesn’t degrade in formulas containing water, 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 amazingly for inflamed pimples.^[7] Magnesium ascorbyl phosphate is considered a stable and effective antioxidant for the skin and usually comes in concentrations around 5%. Its neutral pH makes it easy to formulate with and reduces the chances of sensitivities.

Ascorbyl Palmitate

• Solubility: oil-soluble
• pH: up to 6
• Skin types: sensitive, dry, mature
• Strongest point: reducing UV damage 
• Best at a concentration of: 0.1 to 1%
• What else: Greater stability when encapsulated^[9]

Ascorbyl palmitate is an oil-soluble form of vitamin C, to which is added a fatty acid (palmitic acid) to make it more stable and gentler. Since ascorbyl palmitate is combined with a fatty acid, its hydrating benefits are higher than other types of vitamin C in skincare. 

However, even if it’s soluble in oil and penetrates the skin more in-depth than L-ascorbic acid, its conversion into the pure form of vitamin C may be limited.^[10] As a fat-soluble compound, ascorbyl palmitate is often used in oil-based cosmetics, so if you’re prone to breakouts, ensure the product is non-comedogenic. 

3-O-ethyl-ascorbic acid

• Solubility: oil- and water-soluble
• pH: between 4 and 6
• Skin types: sensitive, dry, mature
• Best at a concentration of: 0.1 to 1%
• Strongest point: brightening
• What else: better than ascorbyl glucoside at getting into the skin

3-O-ethyl-ascorbic acid is a stable derivative of L-ascorbic acid. Due to its solubility in both water and oil, 3-O-ethyl-ascorbic acid has excellent penetration, meaning it can trigger changes in the deeper layer of the skin. This form of vitamin C carries antioxidant, anti-inflammatory, and collagen-boosting benefits, and it’s especially good at brightening the skin as it’s a potent tyrosinase inhibitor.^[11]

Ascorbyl Glucoside

• Solubility: water-soluble
• pH: between 4 and 6
• Skin types: oily, acne-prone, dry, normal, combination
• Best at a concentration of: 0.1 to 1%
• Strongest point: it’s gentle

Ascorbyl glucoside is a form of vitamin C combined with glucose (sugar) that carries all the benefits vitamin C has while being gentler. Since it requires to be converted into the pure form of vitamin C, ascorbyl glucoside is milder, hence more suitable for easily reactive skin. 

Tetrahexyldecyl Ascorbate 

• Solubility: oil-soluble
• pH: lower than 6.5
• Skin types: oily, acne-prone, dry, normal, combination
• Best at a concentration of: 0.1 to 1%
• Strongest point: great skin penetration

Tetrahexyldecyl ascorbate (THD) is a widely used type of vitamin C 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 type of vitamin C in terms of potency, while magnesium ascorbyl phosphate is the most stable form used in skincare. Also, ascorbyl glucoside and ascorbyl palmitate are the best forms of vitamin C for people with sensitive skin

Frequently asked questions