1. Why are you using that retinol and vitamin C?

Are you using them just because they seem “good for your skin”?

Both vitamin C and retinol are staple skincare ingredients. Since you often see their names in social media posts and reviews, it is easy to think, “It’s safe as long as it’s in there.”
However, if asked, “So, what exactly is it doing for your skin?”, you might find it surprisingly difficult to answer.

Actually, retinol and vitamin C have very different roles

Broadly speaking, these two have completely different areas of expertise.
Vitamin C: Protects the skin from “oxidative damage” caused by UV rays and the like, in charge of defense
Retinol: Supports functions related to skin turnover and firmness, in charge of renovation work

Both are widely used ingredients in skincare, but protecting and rebuilding are different types of work. Also, how much they actually work depends significantly on the type, concentration, and formulation of the ingredient.

First, let’s learn “what kind of effect the ingredient is intended to have”

The fact that their roles are different also means you can choose based on “which one suits my concerns.”

Concerned about dullness or UV damage → Lean towards vitamin C
Concerned about firmness, texture, or fine lines → Lean towards retinol

Keeping this perspective in mind will make choosing products much easier.

2. What is vitamin C doing in the morning?

The main role of vitamin C is “antioxidation”

The primary role of vitamin C is “antioxidation.”

When you are exposed to UV rays, unstable substances called “active oxygen (free radicals)” are generated within the skin. It is believed that these damage skin cells and collagen. Vitamin C has the function of neutralizing this active oxygen.[^1]

What happens to the skin when exposed to UV rays?

Skin damage caused by UV rays is not just about getting red from a sunburn. It is known that over a long period of time, it leads to spots, dullness, and a loss of firmness (so-called “photoaging”).

Using vitamin C in the morning is based on the idea of preparing for the oxidative stress caused by the UV rays and outside air you will be exposed to throughout the day.

It is also related to pores, texture, and clarity

In addition to antioxidation, vitamin C also has

is well-known. [^1]

In Japan, some vitamin C derivatives are approved as active ingredients in quasi-drugs (medicated cosmetics) for their efficacy in “suppressing melanin production and preventing spots and freckles.”

However, this does not promise dramatic changes such as “pores disappearing” or “spots vanishing.” It is best to think of it as an ingredient for “prevention and support” in your daily care.

Note: “Vitamin C derivatives” like C10 are modified forms designed to stabilize vitamin C (ascorbic acid), which is otherwise easily broken down. While they are expected to function as vitamin C within the skin, the efficiency of their conversion varies depending on the type of derivative, and there is less research on them compared to pure vitamin C. [^1]

https://pmc.ncbi.nlm.nih.gov/articles/PMC5605218/

However, it is not a substitute for sunscreen

This is an important point.

The job of vitamin C is to neutralize reactive oxygen species that have already formed. Since its mechanism is different from sunscreen, which blocks ultraviolet rays themselves, it cannot replace sunscreen. Even in research papers, it is positioned as a way to “supplement oxidative damage that cannot be fully prevented by sunscreen alone.” [^1]

I think it is best to imagine morning vitamin C as a “defensive substitute player placed under your sunscreen.”

Vitamin C = morning defense. But the ace is sunscreen.

3. What does retinol do at night?

Retinol is an ingredient that helps with “renovation work” for the skin

Retinol is a type of vitamin A. It is thought to change into retinal and then retinoic acid within the skin, where it plays a role in skin cell turnover and collagen production. [^2][^3]

In other words, it is like supporting the skin renovation work that takes place while you sleep.

Effects on firmness, texture, and fine lines

In a study targeting elderly individuals, it was reported that a group that applied 0.4% pure retinol consistently for 24 weeks saw an improvement in fine lines. [^2]

In Japan, quasi-drugs containing retinol as an active ingredient for “improving wrinkles” have also been approved.

However, this is only if used properly for a set period at a specific concentration and formulation. It does not guarantee that the products you have on hand will yield the same results.

Results do not appear immediately

Since this is renovation work, it is not something that will be completed in a day or two. In the aforementioned study as well, the evaluation was done over a period of months.[^2]

It is an ingredient that would be a waste to give up on after saying, “I used it for a week but nothing changed.”

Beware of irritation, dryness, and peeling

When you first start using retinol, you may experience

• redness

• dryness

• peeling

• tingling sensations

.[^3][^4] This is not “proof that it is working,” but rather a reaction (side effect) to irritation. Medically, it is sometimes called “retinoid dermatitis.”

It is commonly referred to as “A-reaction,” but there is no need to endure strong irritation and continue using it.

• Start with a low frequency, such as once every 2 to 3 days at first

• Do not be greedy with the amount

• Moisturize thoroughly

It is common to let your skin get used to it using methods such as these.

Also, regarding medical-grade retinoids, there is literature that suggests they should be avoided during pregnancy.[^4] If you are pregnant or breastfeeding, it is safer to consult a doctor in advance even for cosmetic retinol.

Retinol = night shift work. Do not rush, take it little by little.

4. Why vitamin C is for the morning and retinol is for the night

Morning is for protection against UV rays and oxidative stress

To summarize what has been discussed so far, the reason is simple.

Since vitamin C is an “ingredient that prepares you for damage you are about to receive,” its role is easier to understand when used in the morning before being exposed to UV rays.

Retinol is easier to use at night considering light and irritation

There are mainly two reasons why retinol is often used at night.

1. Some members of the retinol family (retinoids) are easily broken down by light [^4]

2. When you first start using it, it is prone to causing irritation and dryness, making the skin more sensitive [^4]

It is more logical to use it at night and let it work thoroughly rather than using it during the day amidst UV rays.

Also, while you are using retinol, sunscreen the next morning is more important than ever.

There is no problem with using vitamin C at night

This is something that is surprisingly not well known.

Vitamin C is not an ingredient that must not be used at night. Its antioxidant and melanin-inhibiting effects can be expected both in the morning and at night.

For those who say, “I’m too busy in the morning to have time to apply it,” using it at night is one option.

It is not a case of “it must be morning” or “it won’t work unless it’s at night”

“Vitamin C in the morning, retinol at night” is a “convenient time to use” thought of based on the properties of each.

It is not an absolute rule, and it is fine to just remember it as:

• Vitamin C: When used in the morning, it easily fits the role of daytime protection

• Retinol: It is safer to use at night due to light and irritation

that much is fine.

5. Can retinol and vitamin C be used together?

Using both is fine. But there is no need to layer them at the same time

To start with the conclusion, it is fine to use both vitamin C and retinol in your daily skincare routine.

However, “using both” here means using them at different times, such as vitamin C in the morning and retinol at night. It does not mean layering them at the same time. You may see talk online that “using them together cancels out their effects,” but as far as I have researched, I have not found any clear evidence to support that.

On the other hand, I could not find any evidence that layering them together increases their effectiveness. Since both are ingredients that can cause irritation, layering them unnecessarily might only increase the burden on your skin.

Separating them into morning and night is the simplest approach

Vitamin C in the morning, retinol at night. This way of separating them has the following benefits:

It is easier to tell which one is the cause if irritation occurs
You can match them to their respective optimal times (Vitamin C for daytime defense, retinol for nighttime repair)
Since you are layering fewer ingredients at once, it is easier to reduce the burden on your skin

Ultimately, the common advice to use them separately is the most straightforward approach.

Don’t push yourself if you feel irritation

If you experience redness or stinging,

• reduce the frequency of retinol

• take a break from one or both for a while

• consult a dermatologist if symptoms persist

and other such measures are important to avoid overdoing it.

Skincare is not a case of “the more, the better”

Active ingredients do not work faster just because you apply more of them. In fact, it can increase irritation and even damage your skin’s barrier.

Consistency every day with an amount and frequency you can maintain.This is the best shortcut.

6. You can choose skincare based on “ingredients and purpose” rather than brand

Focus on “what is the purpose of using it” rather than the brand name

After reading this far, you will see that what is important is not “which brand” but rather

I think it has become clear that this is the case.

I want to use vitamin C-based ingredients in the morning,
I want to use retinol-based ingredients at night

If you think this way, you will be able to compare other products as well.

Products sold on e-commerce sites are easy to obtain and often reasonably priced, which is a major advantage for maintaining a routine.

Knowing that there are other options for the same purpose also expands the fun of choosing.

So next, I will compare them based on ingredients, price, and ease of use, rather than brand name.

Don’t choose retinol based on concentration alone

When choosing retinol-based products, it is recommended to check not only the concentration number, but also:

• Type of ingredient: Is it retinol (pure retinol) or a derivative like retinyl palmitate?

• Consideration for irritation: Is it a low concentration for beginners, or for those who are used to it?

• Container: Is it a container that is resistant to light and air (such as a tube or airless container)?

as well.

Vitamin C is also not “all the same if it’s 10%”

Vitamin C is the same; even if it says “10% formulation”,

• Is it pure vitamin C (ascorbic acid)?

• What type of vitamin C derivative is it (APPS, VC-ethyl, ascorbyl glucoside, etc.)?

• What is the 10% based on? (Labeling methods vary by product)

can significantly change the contents. If you get into the habit of looking at the ingredient list instead of just comparing numbers, you will be less likely to make mistakes.

Let’s compare price, volume, ingredients, and ease of use

Ultimately, it is realistic to compare them based on the following four points.

Price: Not just the base price, but the price per 1mL
Capacity: How many days it lasts
Ingredients: The type of target ingredient and how it is formulated
Ease of use: Texture, scent, lack of irritation, and ease of continuing

7. Cost-effective alternatives you can choose for the same purpose

Recommended candidates for Vitamin C products

15% Vitamin C derivative
MUJI High Concentration Serum with Vitamin C Derivative
A simple option with 15% Vitamin C derivative
Price: 2,490 yen
Capacity: 30mL
Price per 1mL: approx. 83 yen
[View on Amazon]

Moisturizing gel with Vitamin C derivative
Can be used after serum as a substitute for milky lotion or cream
Melano CC Medicated Whitening Gel for Spot Prevention
Price: 991 yen
Capacity: 100g
Price per 1g: approx. 9.9 yen
[View on Amazon]

Pure Vitamin C + 3 types of Vitamin C derivatives
LITS Moist Perfect Rich Gel C Fragrance-Free 90g
Price: 2,178 yen
Capacity: 90g
Price per 1g: approx. 24.2 yen
[View on Amazon]

Recommended candidates for retinol products

0.1% Retinol derivative
MUJI High Concentration All-in-One Serum with Retinol Derivative
Large 100g capacity + all-in-one
Price: 2,990 yen
Capacity: 100g
Price per 1g: approx. 29.9 yen
[View on Amazon]

Nameraka Honpo Wrinkle Gel Cream
N All-in-One Product Soy Milk Isoflavone 100g
Pure retinol + retinyl palmitate (retinol derivative)
Price: 1,880 yen
Capacity: 100g
Price per 1g: approx. 18.8 yen
[View on Amazon]

Contains retinol derivative
AQUALABEL Special Gel Cream EX (Golden Repair)
5-in-1 all-in-one containing the retinol derivative ‘retinyl acetate’
Price: 1,958 yen
Capacity: 90g
Price per 1g: approx. 21.8 yen
[View on Amazon]

If you are satisfied with your current product, there is no need to force a change

I have introduced alternative candidates here, but if your skin is in good condition with your current product and you are able to continue using it, there is no need to force a change.

The most important thing in skincare is to continue using products that suit your skin.

What is important is not to do it ‘just because,’ but to

be in a state where you can explain, ‘I chose this product because I want this ingredient.’

to be able to explain it.I hope this article serves as an opportunity for you to review your daily skincare routine.

I hope this article serves as an opportunity for you to review your daily skincare routine.

Summary

• Vitamin C plays a primary role in anti-oxidation. Using it in the morning fits its role as ‘defense’ against UV rays. However, it is not a substitute for sunscreen.

• Retinol is in charge of ‘nighttime construction’ to support skin turnover and firmness. It is easily broken down by light and can cause irritation, so it is easier to use at night. Expect results over a period of several months.

• It is not that “it must be morning” or “it won’t work at night,” but rather a matter of the most convenient time to use them.

• The two can basically be used together. For beginners, it is easier to understand if you separate them into morning and night.

• Choose products based on ingredients, purpose, price, and ease of continued use rather than brand.

*This article is a summary of information researched by an individual regarding skincare ingredients. Effects vary by individual. If skin problems persist, or if you are pregnant or breastfeeding, please consult a professional such as a dermatologist.

References

[^1]: Al-Niaimi F, Chiang NYZ. Topical Vitamin C and the Skin: Mechanisms of Action and Clinical Applications. J Clin Aesthet Dermatol. 2017;10(7):14-17. https://pmc.ncbi.nlm.nih.gov/articles/PMC5605218/
[^2]: Kafi R, et al. Improvement of naturally aged skin with vitamin A (retinol). Arch Dermatol. 2007;143(5):606-612. https://pubmed.ncbi.nlm.nih.gov/17515510/
[^3]: Oregon State University, Linus Pauling Institute. Vitamin A and Skin Health. https://lpi.oregonstate.edu/mic/health-disease/skin-health/vitamin-A
[^4]: Motamedi M, et al. A Clinician’s Guide to Topical Retinoids. J Cutan Med Surg. (Published online 2021). https://pmc.ncbi.nlm.nih.gov/articles/PMC8750127/
[^5]: Milosheska D, Roškar R. Use of Retinoids in Topical Antiaging Treatments: A Focused Review of Clinical Evidence for Conventional and Nanoformulations. Adv Ther. 2022. https://link.springer.com/article/10.1007/s12325-022-02319-7