Vitamin C is a popular ingredient in many skincare serums. It is a powerful antioxidant that can help brighten skin, reduce signs of aging, and protect against environmental damage. However, vitamin C can become less effective or even degrade when mixed with the wrong ingredients. Knowing what not to combine with vitamin C is important to get the most out of your serums.
Vitamin C Benefits for Skin
Before looking at what not to combine with vitamin C, let’s first understand why it’s such a beneficial ingredient for skin:
- Brightens skin tone and reduces hyperpigmentation
- Increases collagen production to reduce fine lines and wrinkles
- Protects against free radical damage from UV exposure and pollution
- Reduces inflammation and irritation
- Improves moisture content and hydration
These powerful effects make vitamin C a staple in many anti-aging and brightening skincare routines. Using a properly formulated and stable vitamin C serum is key to experiencing these benefits.
Ingredients to Avoid Mixing with Vitamin C
There are a few types of ingredients that can diminish the effectiveness of vitamin C or render it completely ineffective. Here are the main ones to avoid using at the same time as vitamin C:
Benzoyl Peroxide
Benzoyl peroxide is a common acne medication. It works by killing acne-causing bacteria on the skin while exfoliating dead skin cells within pores. However, benzoyl peroxide can oxidize vitamin C when they are applied together, rendering it ineffective.
If using both a vitamin C serum and a benzoyl peroxide product, apply them at different times of day and allow the vitamin C to fully absorb first. For example, use vitamin C in the morning and benzoyl peroxide at night.
Retinoids
Retinoids like retinol and tretinoin (Retin-A) are anti-aging superstars. They speed up cellular turnover to reduce fine lines, wrinkles, acne, and hyperpigmentation. However, retinoids can be deactivated by vitamin C if applied at the same time.
When using both a vitamin C serum and retinoid, apply vitamin C in the morning and the retinoid at night. Let the vitamin C fully absorb before applying anything else.
Niacinamide
Also known as vitamin B3, niacinamide is another popular skincare ingredient. It calms inflammation, strengthens the skin barrier, evens skin tone, and reduces redness. However, some research shows niacinamide can cancel out the benefits of vitamin C when applied simultaneously.
To avoid this interaction, use vitamin C and niacinamide at different times of the day, such as vitamin C in the AM and niacinamide in the PM.
AHAs and BHAs
Alpha hydroxy acids (AHAs) like glycolic and lactic acid plus beta hydroxy acids (BHAs) like salicylic acid are chemical exfoliators. They loosen dead skin cells and unclog pores for a smoother, clearer complexion.
However, the exfoliating effects of AHAs and BHAs make the skin more vulnerable to oxidation. Applying them at the same time as vitamin C could make it penetrate too deeply and irritate the skin.
Use AHAs and BHAs either on alternate days from vitamin C or at a different time of day after it has absorbed.
Hydroquinone
Hydroquinone is a skin-lightening agent used to treat pigmentation disorders like melasma. While hydroquinone and vitamin C both inhibit melanin production, data shows they become degraded when mixed.
If using both ingredients, apply hydroquinone in the morning and vitamin C at night. Do not use one right after the other.
Copper Peptides
Copper peptides are short chains of amino acids that can firm and lift the skin. However, copper peptides may interact with vitamin C and inactivate it before it can provide its antioxidant benefits.
Avoid layering copper peptide products with vitamin C. Instead, use them at different times such as copper peptides in the morning and vitamin C at night.
Oils and Silicones
Oils like jojoba, grapeseed, and marula plus silicones like dimethicone create a hydrophobic barrier on the skin. This can seal out water-soluble ingredients like vitamin C and prevent proper absorption.
When using a vitamin C serum, apply oil-free hydrators and products without silicones first. Then layer vitamin C before finishing with any occlusive moisturizers.
How to Properly Combine Vitamin C
While vitamin C doesn’t mix well with certain ingredients, it works great when paired with others. Some of the best partners for vitamin C include:
- Hyaluronic acid – enhances hydration
- Vitamin E – offers additional antioxidant protection
- Ferulic acid – stabilizes vitamin C
- Alpha lipoic acid – regenerates vitamin C
- Peptides – support collagen production
- Ceramides – reinforce the skin barrier
Look for vitamin C serums formulated with complementary ingredients like these for maximum efficacy and minimal irritation.
Tips for Using Vitamin C Effectively
Follow these best practices to safely use vitamin C serum and experience all of its wonderful brightening, smoothing, and anti-aging perks:
- Do a patch test first to rule out any irritation or allergy.
- Start with a lower vitamin C concentration around 5-10% and build up gradually to 20% max.
- Apply vitamin C after cleansing and toning but before heavier moisturizers.
- Allow vitamin C to fully absorb for 10-15 minutes before applying other products.
- Use vitamin C in the morning for best photoprotection throughout the day.
- Store vitamin C serums in opaque packaging and refrigerate after opening.
- Discontinue use if skin becomes red, itchy, or irritated.
Frequently Asked Questions
Why does vitamin C degrade so quickly?
In its pure form, vitamin C (L-ascorbic acid) is highly unstable. When exposed to light, air, or certain ingredients, it rapidly oxidizes and becomes less effective. Using properly formulated serums with vitamin C derivatives and stabilizers helps prevent degradation.
What percentage of vitamin C is most effective?
Studies show vitamin C concentrations between 10-20% provide the most benefits for skin health, collagen production, and fighting signs of aging. Anything above 20% may lead to irritation without added effect.
Can vitamin C serum lighten skin?
Yes, vitamin C is a mild skin-lightening agent. By limiting melanin production in the skin, vitamin C serum can lighten hyperpigmentation and create a more even skin tone over time.
Is it better to use vitamin C in the morning or at night?
Most dermatologists recommend using vitamin C serum in the morning. This allows it to neutralize free radicals from sun and pollution exposure during the day. At night, pair vitamin C with retinoids or gentler antioxidants like niacinamide.
How do you know if a vitamin C serum has gone bad?
Signs that a vitamin C serum has oxidized and expired include a yellow or brown color, separation in the bottle, and a completely clear consistency. Ideally, vitamin C serums should be opaque and cream or gel-like.
The Bottom Line
Vitamin C provides incredible benefits for skin health and a more youthful, radiant complexion. However, it can easily degrade and become ineffective when mixed with certain ingredients like benzoyl peroxide, retinoids, and AHAs. Always apply vitamin C on its own first and give it time to fully absorb before layering on other products.
With a bit of awareness about what not to combine it with, you can safely maximize the perks of vitamin C for glowing skin all year long.