Ascorbic acid, also known as vitamin C, was originally discovered during research into the causes and treatment of scurvy. It plays an essential role in human physiology by acting as a water-soluble antioxidant that removes reactive oxygen species (ROS) or free radicals. Ascorbic acid helpful in preserving important molecules in our body by keeping them in a safe and stable form. Additionally, it assists enzymes (which are important proteins that help our body do important tasks) in their work by making it easier for them to do their job. It does this by helping to reduce metal ions that may be blocking the enzyme’s active site, kind of like clearing a path for the enzyme to do its task well.

Unlike plants and some animals, humans cannot synthesize ascorbic acid because we lack a specific enzyme that’s needed for its production. This means that we have to get our vitamin C from outside sources, such as fruits, vegetables, supplements, – and topical skincare.

Collagen is the most abundant protein in our body and is a major component of the skin’s extracellular matrix, and ascorbic acid plays an important role at multiple stages in collagen production.

It’s also important to note that ascorbic acid can be unstable and easily degraded when exposed to air, light, and heat. Therefore, it’s essential to choose a stabilized form of ascorbic acid that can penetrate the skin effectively and remain active for an extended period.

Skincare formulators use various techniques to stabilize ascorbic acid and improve its delivery to the skin in topical products. Some of the common techniques are:

• pH Adjustment: Ascorbic acid is most stable at a pH range of 2.5 to 3.5. Skincare formulators adjust the pH of the formulation to this range to improve the stability of ascorbic acid.
• Packaging:  ascorbic acid products in opaque or airless containers protects them from light and air exposure.
• Antioxidants: adding other antioxidants, such as vitamin E and ferulic acid, to ascorbic acid formulations improves their stability and enhances efficacy.
• Microencapsulation: Skincare formulators use microencapsulation technology to encapsulate ascorbic acid in a protective shell, which prevents it from degrading and improves its delivery to the skin.
• Liposomes: Liposomes can encapsulate ascorbic acid and deliver it deep into the skin. Liposomes are small vesicles made up of phospholipids that can penetrate the skin effectively and deliver active ingredients.

Formulators also often use various derivatives of ascorbic acid, such as ascorbyl palmitate, ascorbyl tetraisopalmitate, magnesium ascorbyl phosphate, and sodium ascorbyl phosphate instead of pure ascorbic acid. Derivatives of ascorbic acid offer several benefits, including improved stability and better penetration into the skin. Unfortunately though, the derivatives do not seem to work as well  in skin and pure ascorbic acid remains a better choice in skincare if you are looking for an anti-aging effect.

A study conducted by Rhie et al. reported that the levels of ascorbic acid in the skin of both photoaged and naturally aged skin were lower compared to young skin. This suggests that external supplementation of ascorbic acid may help slow down the aging process in the skin. Clinical trials have been conducted to determine whether the topical application of ascorbic acid can increase collagen in the skin. Collagen is a protein that gives the skin its structure and elasticity.

In one study, 10 postmenopausal women applied a cream containing 5% ascorbic acid on one side of their upper forearm and a placebo on the other side. After six months of nightly use, the mRNA levels of collagen type I and type III in the skin biopsy were increased in the ascorbic acid-treated groups. However, there was no significant difference observed in the concentration of collagen extractable from the skin.

In another clinical trial, 19 subjects applied a 5% ascorbic acid cream twice a day to the extensor surface of one forearm for two weeks. Statistical analysis of all the subjects did not show a significant increase in procollagen level compared to the baseline before treatment. However, when the subjects were divided into a group with a low baseline procollagen I level and a group with a high baseline procollagen I level, the former group showed a significant increase in procollagen I level with ascorbic acid cream application. This suggests that ascorbic acid helps to increase collagen in the skin, especially or only when there is a lack of ascorbic acid or collagen.

In a randomized, double-blind, placebo-controlled study, 19 healthy female volunteers applied 5% ascorbic acid cream on the sun-exposed upper chest and forearm once a day for six months. The results showed that the application of ascorbic acid cream significantly increased the density of skin microrelief, decreased deep furrows, and improved the ultrastructure of the skin compared to the placebo treatment.

Another study enrolled 20 women with photo-aged skin and applied 23.8% ascorbic acid serum with iontophoresis on one side of the face once a day for two weeks. The results showed that the treatment significantly improved hyperpigmentation, surface roughness, and fine lines on the treated side compared to the other side that was spared for participants’ self-control.

In a double-blind, split-face, placebo-controlled clinical study, a dissolving microneedle patch containing ascorbic acid was applied around crow’s feet on one side of the face and a placebo patch on the other side for 12 weeks in 23 subjects with notable wrinkles near the eyes. The results showed that the ascorbic acid-loaded dissolving microneedle patch significantly reduced wrinkles in the crow’s feet area without causing skin irritation and sensitization problems.

In a double-blind, prospective, randomized clinical trial, patients underwent laser skin resurfacing procedure followed by topical treatment of 200 mg ascorbic acid with or without a cosmeceutical containing growth factors. Three months after the treatments, there was a significant reduction in skin roughness and the average depth of periorbital wrinkles in both groups. The group treated with ascorbic acid plus growth factors showed better results compared to the group treated with ascorbic acid alone.

While these studies suggest that ascorbic acid can help alleviate the symptoms of skin aging, it’s important to note that the number of studies conducted is not considered sufficient to confirm its efficacy. Additionally, the concentration of ascorbic acid used in the studies varies, and more research is needed to determine the optimal concentration and frequency of use.

The length of time it takes to see results from ascorbic acid skincare products varies depending on several factors, including the concentration of ascorbic acid, the formulation of the product, and the individual’s skin type and condition. Generally, it can take several weeks to several months to see noticeable improvements in the skin’s appearance and texture.

In some clinical trials, improvements in the skin were observed after six months of consistent use of ascorbic acid skincare products. However, some people may see improvements in their skin’s appearance after just a few weeks of use. It’s important to note that individual results may vary, and consistent use of ascorbic acid skincare products is necessary to maintain the benefits over time.

It’s also essential to remember that skincare products containing ascorbic acid work best when used in combination with other skincare practices, such as daily sun protection and balanced nutrition.

While ascorbic acid is a potent antioxidant that offers numerous benefits for the skin, it can also cause skin irritation, especially for those with sensitive skin. Ascorbic acid is an acidic molecule and can cause stinging, burning, and redness when applied topically. The risk of irritation can be increased if the concentration of ascorbic acid is too high or if the formulation contains other ingredients that can be irritating to the skin. To minimize the risk of irritation, patch-test new ascorbic acid products on a small area of the skin before applying them to the entire face. If your skin is sensitive, start  with a low concentration of ascorbic acid and gradually increase it over time as the skin tolerates it. If skin irritation occurs, discontinue the product: there is no benefit in “pushing through” the irritation. Ascorbic acid also does not cause “purging”. 

Generally, concentrations between 5% to 20% have been shown to be effective in improving the appearance of the skin. However, higher concentrations of ascorbic acid can increase the risk of skin irritation.

In terms of frequency of use, it’s recommended to use ascorbic acid skincare products once or twice a day, depending on your skin’s sensitivity and other actives in your routine (use ascorbic acid less frequenlty if you are also using other potentially irritating actives like retinoids). Applying ascorbic acid products in the morning can provide added protection against environmental stressors such as UV radiation, while applying them at night can help promote photodamage repair.