How long to wait after applying Vitamin C serum before using the next product in your skin care routine depends upon which type of serum you are using.

The best Vitamin C serums are backed in amber colored bottles and are a low pH. These penetrate the fastest- much faster than Vitamin C creams or lotions.

Serums can be very expensive, so you do not want to do anything to decrease penetration of ascorbic acid!

If Vitamin C serums are applied to skin that has just been cleansed with a low pH cleanser, rinsed with warm water, and is still damp, absorption will be faster.

We do not really know how long it takes for the Vitamin C to get into the skin. Studies on this are detailed below.

10 things that determine how fast Vitamin C absorbs into the skin:

1. How strong your skin barrier is
2. Temperature of water you used to wash your face
3. If your skin is damp or dry when Vitamin C is applied
4. What you apply to skin before using the Vitamin C
5. What type of Vitamin C you use- serum, cream or lotion
6. Type of moisturizer you use after the vitamin C
7. If you are also using a hyaluronic acid serum in your routine
8. What other products are in your skin care routine
9. What step of the routine you use Vitamin C in
10. If you are using retinol

The original studies to see if topical Vitamin C can be absorbed through the skin were done by Dr. Sheldon Pinnell in 2001. ⁽¹⁾ These absorption studies demonstrated that ascorbic acid 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 after one application. 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.

Dry Baumann Skin Types will absorb Vitamin C better than Oily Baumann Skin Types because dry types have an impaired skin barrier.

You can find out your skin type here

It is best to apply a moisturizer or oil after the vitamin C serum to cause occlusion (also known as skin slugging). Moisturizers can make Vitamin C absorb faster.

Moisturizers can raise the skin pH which decreases absorption of Vitamin C.

Moisturizers with hyaluronic acid and oleic acid (olive oil) will increase absorption.

The type of moisturizer used greatly affects the rate of absorption of all serums.

This is one of the many reasons why you need a skin care routine customized for your Baumann Skin Type.

Skin that is more hydrated or is still wet after cleansing will allow Vitamin C to absorb faster.

Use warm water and apply Vitamin C serum to skin that is still damp but not dripping.

Ingredients such as fatty acids and glycosaminoglycans can affect how fast Vitamin C absorbs into the skin.

If these ingredients are in the Vitamin C serum or in the moisturizer applied afterward, the ascorbic acid will absorb faster.

These ingredients can speed absorption of vitamin C:

glycerin

heparan sulfate

hyaluronic acid

olive oil (if used after the Vitamin C)

propylene glycol

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 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. 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 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.

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).

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.

The type of water you use to wash your face also affects how well skin care products get into the skin.

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. We have already taken all of the above issues into account.

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.

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.

References on Vitamin C absorption rates in skin:

1. 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.
2. Baumann L. Ch 40 Cleansing Agents in Baumann’s Cosmetic Dermatology Ed. 3 (McGraw Hill 2022)