How Long Does it Take for Vitamin C to Absorb Into the Skin?
The original topical Vitamin C absorption studies by Dr. Sheldon Pinnell in 2001[i] demonstrated that ascorbic acid (Vitamin C) absorbs into skin best at a pH of 2- 2.5.
These studies left the ascorbic acid on the skin for 22-24 days and the ascorbic acid was mixed with hyaluronic acid which increases penetration. This does not translate well into how we use our serums every day. So the only published evidence-based study does not answer the question.
There are no published studies that look at how fast Vitamin C absorbs into the skin. So- we really have no idea how long it takes. We do know that it is not easy to get Vitamin C to absorb in the skin- so we need to use every tip and trick to increase Vitamin C absorption.
Many factors affect Vitamin C absorption rates. One of them is your Baumann Skin Type.
What plays a role in how fast Vitamin C absorbs into the skin?
Damp vs Dry Skin
Skin that is more hydrated or is still wet after cleansing will allow Vitamin C to absorb faster.
Other Ingredients Affect Absorption
Other ingredients such as the fatty acid oleic acid and the glycosaminoglycan hyaluronic acid are known to be good penetration enhancers. If these ingredients are in the Vitamin C serum or in the moisturizer applied afterward, the ascorbic acid will absorb faster.
Slugging the Skin with Occlusives Speeds Absorption
Occluding the serum by covering it with a moisturizer containing occlusive ingredients, otherwise known as slugging, will increase absorption. You can read more about slugging here.
The pH of the Skin Affects Absorption
The pH of the skin greatly affects the absorption of Vitamin C as shown in the 2001 study by Dr. Pinnell. Cleansers change the pH of your skin.[ii]
If you are going to use a Vitamin C serum, you must use a low pH cleanser when possible. For example, hydroxy acid cleansers can lower the pH of your skin into the 2- 3.5 range- depending on the cleanser's characteristics. Note that not all Baumann Skin Types can use a low pH cleanser because of the stinging and facial redness that can occur.
In your customized skin care routine that we give you after taking the quiz, we often use a low pH cleanser prior to applying the Vitamin C serum to boost absorption. Which cleanser we choose depends upon your Baumann Skin Type. After you take the quiz, you will be given a list of cleansers from many brands to choose from, but they have all been chosen to help increase the absorption of Vitamin C if it's recommended as part of your personalized skin care routine.
The integrity of Your Skin Barrier
The strength and integrity of your skin barrier will also affect how much vitamin C gets into your skin. A defective skin barrier allows ingredients to pass through the skin more easily. This is why your skin gets irritated easily when you have an impaired barrier.
Condition of your Stratum Corneum
The stratum corneum, the top layer of the skin, also affects how much and how quickly a skincare ingredient can pass through the skin. Using chemical or mechanical exfoliation prior to a Vitamin C serum will thin the stratum corneum allowing more penetration. This is another reason a low pH cleanser prior to a Vitamin C serum is a good idea. (Unless you have one of the sensitive skin types that should avoid low pH cleansers).
Skin Temperature And The Water You Cleanse Face With
The temperature of your skin also affects the penetration of ingredients. Warmer temperatures such as using warm water when cleansing your face will increase penetration and speed absorption of Vitamin C into your skin. If you just took a hot shower, Vitamin C will absorb faster if your skin is still warm.
So- How long does it take Vitamin C to absorb into the skin?
It depends on your entire skin care routine and your Baumann Skin Type!
How Long Do I Wait after Applying Vitamin C to Apply Moisturizer?
The Skin Type Solutions skin care routines are designed so you do not have to wait for the serum to absorb after applying a Vitamin C serum. In fact, we want you to apply the Vitamin C serum to damp skin after cleansing with warm water. Immediately after applying the ascorbic acid serum, you should apply a moisturizer with occlusive ingredients. This helps prevent evaporation of the serum and “Slugs” the Vitamin C into the skin.
Of course- you must use the correct moisturizer and cleanser to get the most out of your Vitamin C serum. These serums are expensive, so we want to help you get your money's worth out of them.
My advice as a dermatologist and skin care researcher is to take the quiz to find out your Baumann Skin Type and follow our skin care routine steps. When you choose products from our recommended list, you can be sure that we have designed the skin care routine steps and recommended products to increase the absorption of Vitamin C.
[i] Pinnell, S. R., Yang, H., Omar, M., Riviere, N. M., Debuys, H. V., Walker, L. C., ... & Levine, M. (2001). Topical L‐ascorbic acid: percutaneous absorption studies. Dermatologic Surgery, 27(2), 137-142.
[ii] Baumann L. Ch 40 Cleansing Agents in Baumann’s Cosmetic Dermatology Ed. 3 (McGraw Hill 2022)