Vitamin C in summer? Absolutely!

In summer, skincare routines are often reduced to the essentials: gentle cleansing, a light moisturizer, and of course, sunscreen. However, one thing that's frequently overlooked is that vitamin C shouldn't be missing from your daily routine, even in the warmer months. Those who neglect it are missing out on one of the most effective active ingredients in their routine.

Many people are hesitant to use active ingredients in products when exposed to strong sunlight – for fear of irritation or sensitivity. However, modern vitamin C formulations are designed to be well-tolerated even at high temperatures and under strong UV exposure.

When used correctly, vitamin C not only provides additional protection for the skin against environmental influences, but also visibly contributes to the radiance and evenness of the complexion – even on hot summer days.

Why Vitamin C?

Vitamin C is one of those ingredients you constantly hear about – but few people really know what it's all about. Sure, it's supposed to have a "brightening" and "anti-aging" effect. But what does that actually mean in concrete terms? Especially when it's 32°C outside and you have to reapply sunscreen several times a day?

Here is the short version:

Vitamin C is an antioxidant – and antioxidants protect the skin from oxidative stress. This is caused by things like UV radiation, pollution, and other external factors. While vitamin C is certainly no substitute for sunscreen (SPF is and remains essential!), it plays an important supporting role.

When applied in the morning under sunscreen, vitamin C provides the skin with an additional protective layer. It helps to neutralize free radicals generated by UV rays – before they can break down collagen, cause age spots, or trigger inflammation.

Why Vitamin C harmonizes perfectly with sunscreen

Vitamin C can do something that sunscreen alone cannot: it neutralizes free radicals. These unstable molecules are produced in large quantities when the skin is exposed to UV radiation, pollution, or even intense heat. Studies show that vitamin C, in combination with sunscreen, reduces UV-induced skin damage by 40–60% compared to using SPF alone.

Think of it this way: sunscreen is the shield that deflects UV rays, while vitamin C is the cleanup crew – repairing any damage that still gets through. Together, they form a powerful duo that protects and strengthens the skin in the long term.

Strengthen collagen for firmer, more youthful skin

From around the mid-twenties, the skin loses approximately 1% of its natural collagen annually – a process further accelerated by sun exposure. UVA and UVB rays attack collagen and elastin fibers, which can lead to wrinkles, sagging skin, and an uneven texture in the long term.

This is where vitamin C comes in: This active ingredient not only helps protect existing collagen, but also actively supports its regeneration. Studies show that vitamin C promotes the enzymes responsible for collagen production and simultaneously helps stabilize existing collagen fibers. The result: firmer, more resilient skin with greater elasticity – even under the summer sun.

More radiant, even skin

Pigment spots caused by sun exposure, old acne scars, or hormonal changes such as those during pregnancy tend to worsen in the summer. Vitamin C counteracts this by regulating melanin production in the skin. This allows dark spots to gradually lighten, resulting in a more even, clearer, and radiant complexion, all without harsh ingredients.

Soothe inflammation

Summer skin is often unpredictable: one day it feels tight, the next it's shiny or suddenly prone to blemishes. This is where vitamin C demonstrates another strength: the active ingredient has anti-inflammatory properties and can also regulate sebum production – particularly helpful when humidity rises or the skin is thrown off balance by sun, sweat, and heat.

Clinical studies also show that vitamin C serums can visibly reduce redness and blemishes in the long term. For many, it's precisely the active ingredient they didn't realize their summer skin had been missing.

But isn't vitamin C too irritating in summer?

This concern is often heard – especially from people with sensitive or easily reactive skin. And it's not unfounded. Because: Not all vitamin C products are created equal.

Some formulations are too concentrated, poorly stabilized, or simply not designed to be skin-friendly. But if you opt for a gentle, well-tolerated alternative – especially from Korean brands, which are known for their sensitive formulations – the skin feels completely different.

A good vitamin C product shouldn't burn, sting, or worsen your skin. If it does, it's simply not the right product for your skin.

Finding the right formulation for hot summer days

Especially in summer, it's important to choose a vitamin C formula that remains stable and effective even in the heat. Not every product is suitable for this – so it's worth taking a close look. Pay attention to the following points:

• Stabilized forms of vitamin C – such as magnesium ascorbyl phosphate (MAP) or encapsulated vitamin C – are effective even at high temperatures.

• The right concentration: Between 10 and 20% L-ascorbic acid is considered effective, while more sensitive skin often responds better to lower dosed derivatives.

• Protective packaging: Opaque, airtight bottles prevent the vitamin C from oxidizing due to light or air and losing its effectiveness.

• Additional antioxidants: Active ingredients such as vitamin E or ferulic acid enhance the antioxidant effect and make the formula even more effective in fighting free radicals.

With the right choice, vitamin C can be used without hesitation even in the height of summer – as the perfect partner for sun protection and as an invisible bodyguard for your skin.

Our top vitamin C favorites for the summer at Seoul Onni

Of course, we've also curated four selected vitamin C products for you , which you can buy directly from Seoul Onni. Each of these products impresses with effective formulations, uncomplicated application, and pleasant textures that are ideal for summer.

Medicube – Deep Vita C Capsule Cream

Our latest insider tip for your summer glow: The Deep Vita C Capsule Cream from Medicube.

It contains a 13.5% stabilized vitamin C blend, embedded in lightweight liposome capsules – supplemented with niacinamide, ferulic acid, vitamin E and sea buckthorn extract.

Clinical studies show impressive results: +34.8% more glow and a visible reduction of pigment spots by 12.9% within 7 days.

Ideal for anyone struggling with dull skin, hyperpigmentation or the first signs of skin aging – or simply wanting to make their complexion visibly glow.

Dear Klairs – Freshly Juiced Vitamin C Drop

A true classic among gentle vitamin C products: Klairs' Freshly Juiced Vitamin C Drop Serum contains 5% L-ascorbic acid – gentle enough for beginners and sensitive skin types.

The texture is light, absorbs quickly and can be easily applied under sunscreen – making it ideal for the morning routine in summer.

Perfect for anyone trying Vitamin C for the first time or looking for a low-irritant, reliable solution.

LoloVegan – Vita Glow Line (Serum & Cream)

The LoloVegan brand is not only completely vegan and cruelty-free , but also impresses with effective, skin-friendly formulations.

The Vita Glow line , consisting of a serum and a cream, contains two vitamin C derivatives: ascorbic acid and ascorbyl tetraisopalmitate – supplemented by niacinamide and snow mushroom extract.

This means: a noticeable moisture boost , gentle soothing through green active ingredients – all in a non-sticky, summer-friendly texture.

Suitable for virtually every skin type. The products can be used individually or – for best results – perfectly in combination.

Pro tips: How to get the most out of your vitamin C in summer

Finally, we'd like to give you a few small but effective tips to make your vitamin C use in summer even more effective and safer. Because often it's precisely these details that make all the difference:

Apply in the morning after cleansing

Vitamin C works best when applied directly to cleansed skin – before moisturizer or sunscreen. After washing, gently pat your face dry and apply the serum as the first step in your skincare routine.

Store correctly

Vitamin C is a sensitive active ingredient and reacts sensitively to light and heat. To prevent your serum from oxidizing (which is indicated by a brownish or yellowish color and reduces its effectiveness), you should store it in a cool, dark place.

Caution with strong active ingredients

Those who use other active ingredients such as AHAs, BHAs, or retinoids in addition to vitamin C should be careful with layering. This combination can quickly lead to irritation, especially for sensitive or untrained skin.

Ideally: Vitamin C in the morning, other active ingredients in the evening. This will keep your skin balanced.

Sun protection is a must

As powerful as vitamin C is, it doesn't replace SPF. For optimal protection, you should always use a sunscreen with at least SPF 30 over your vitamin C serum.

And: Even when it's cloudy outside, UV rays still reach your skin. Therefore, especially in summer, it's important to reapply sunscreen regularly, ideally every two hours if you spend a lot of time outdoors.