A new serum sometimes brings with it more questions than its small bottle suggests. Morning or evening? Before the cream? And does it really belong in the fridge?

When it comes to vitamin C, it is particularly worth taking a look at the specific product. The same capital letter can have different ingredients and recipes. If you separate them a little, the application will become clearer.

What do you mean by “Vitamin C”?

In an ingredient list, Ascorbic Acid denotes ascorbic acid. You will also come across related forms, so-called derivatives, such as 3-O-Ethyl Ascorbic Acid . They are chemically modified and differ, among other things, in their formulation properties. COSRX R&D: Vitamin C forms

Therefore, percentages of different forms cannot simply be equated. The absorption into the skin also depends on the recipe. An experimental study with pig skin has already shown that formulation conditions and the form of vitamin C examined make a difference. It does not provide a universal ranking of all serums today. Pinnell et al.: Absorption of ascorbic acid

This is quite relieving information for your shopping: you don’t have to find the bottle with the largest number. First of all, it’s about what form is included and how the product should be used.

What is vitamin C used for?

Vitamin C is used, among other things, for a more even skin tone and for visible signs of photoaging. In a controlled study, a cream with five percent vitamin C was tested on photo-aged skin for six months. The researchers found improvements in the skin’s appearance compared to the comparison cream. This is a proof of this application, not a promise of the result of any serum. Humbert et al.: Controlled vitamin C study

Antioxidant care does not replace sun protection. Even if it says “Vitamin C” on the bottle, your morning routine needs its own sun protection step. The AAD lists vitamin C as a possible addition to a sunscreen base. AAD: Care and sun protection

If you are primarily concerned with traces of pimples, our article on pimple marks and pigment spots will help first. Not every color change has the same cause.

An example: COSRX The Vitamin C 13 Serum

According to the published list of ingredients , the COSRX The Vitamin C 13 Serum contains 13 percent ascorbic acid . There are also a vitamin C derivative, panthenol, sodium hyaluronate, allantoin and niacinamide. The percentage here refers to ascorbic acid. Bloom & Shine: product and ingredients

The shop lists a few drops for this serum after cleansing and, if necessary, toner; Sun protection follows during the day. You don’t need to reintroduce toner for this. The decisive factor is the place of the serum within your existing care routine and the instructions on your package. Bloom & Shine: Application

When weighing up between lighter and richer care, it helps to look at the entire routine. Maybe the cream is already rich enough, maybe you want as few layers as possible in the morning. Both can be taken into account in the decision.

You can find vitamin C care and complementary products for a fresh-looking complexion at Revitalize a dull complexion .

Start over without changing everything right away

First try out a new product on a small area of ​​skin. The AAD recommends seven to ten days and application according to the product instructions. If there is a significant reaction, the product is washed off and no longer used. AAD: Test care in advance

During this time, keep your other care as clear as possible. When a new peeling, a new cream and a serum are added at the same time, it is difficult to attribute the feeling on the skin to a single step. You can take your time with the selection and first observe how the first addition feels.

If your skin is already irritated, it will help you first to classify tension, burning and skin barrier .

What about niacinamide and retinol?

Niacinamide is already included together with vitamin C in the COSRX formulation mentioned. This shows why a blanket ban on combining both ingredients is not very helpful. However, it doesn’t say whether any two finished products will work well together for your skin.

If you are considering additional niacinamide serum , consider this possible dual need first. You don’t have to have every interesting ingredient in its own bottle.

With retinol or retinal , tolerability is an important question. Retinoid care can be irritating; the AAD recommends a careful start. Getting to know new active ingredient products one at a time is therefore more manageable than immediately packing them into the same evening. AAD: Retinoid or Retinol?

Which place is right for the bottle?

COSRX recommends storing its highly concentrated ascorbic acid serums, including vitamin C 13, in the refrigerator. The manufacturer also recommends closing the pipette bottle after use and avoiding heat and direct sun. Please note the shelf life and instructions after opening. This is a recommendation for these COSRX formulations, not a refrigerator requirement for all vitamin C products. COSRX R&D: Vitamin C Product Guide

Write the opening date on the packaging if necessary. If you later notice that the color, smell or consistency has changed, asking with the product name and photo will be more helpful than a general color table from the Internet.

What we know for sure

• Ascorbic acid and vitamin C derivatives cannot be compared interchangeably.
• Study results relate to specific formulations and applications.
• Vitamin C complements the care; Sun protection remains a separate step.
• Application and storage depend on the respective product.

You can find more terms in our overview Ingredients in K-Beauty .

Sources

• Pinnell et al. (2001): Topical L-ascorbic acid: percutaneous absorption studies
• Humbert et al. (2003): Topical ascorbic acid on photoaged skin
• AAD: Dermatologist-recommended skincare for your 20s
• Bloom & Shine: COSRX The Vitamin C 13 Serum
• COSRX R&D Center: All about Vitamin C
• AAD: How to test skincare products
• AAD: Retinoid or retinol?

Vitamin C in the morning or evening?

Both are possible; Product instructions and compatibility are crucial. Vitamin C is often used in the morning with sun protection. In the evening it can also fit into the routine. Do not start using a retinoid and an acid peel at the same time if you don’t know your reaction yet.

If a vitamin C serum burns significantly or persistently, continue reading Vitamin C Burns: What Helps Now. You can look up individual INCI names in our tool Understanding Ingredients .

Want to try vitamin C for dark pimple marks? A single serum for a more even-looking complexion is enough as a new step to get to know each other. Plan sun protection: It is part of the care for pigment spots , even if you use your serum in the evening.

Continue with your care

• Discover care Glass Skin
• Discover care Balance skin tone
• Your selection guide Find your routine