Vitamin C Serum: Why It Works, and Why Pro Helix C Goes Further
Few skincare ingredients have earned their place quite like vitamin C. It brightens, it protects, and it sits at the heart of how skin builds collagen.
Used every morning, a well formulated vitamin C serum helps defend skin against everyday environmental stress, brings back radiance and supports the collagen that keeps skin firm. The Skin Diary Pro Helix C, the brand's first ever vitamin C serum, builds on those benefits with collagen signalling peptides designed to support firmness and elasticity, in a formula gentle enough for sensitive skin.
What are the benefits of vitamin C for skin?
Vitamin C is one of the most important antioxidants in the upper layers of the skin. Every day, UV exposure and pollution generate free radicals that contribute to visible ageing. Vitamin C helps neutralise them, which is why dermatologists so often recommend it as the first active in a morning routine.
It also has a role in evening out tone and the look of pigmentation, giving skin that brighter, more even quality most people notice within the first week or two of consistent use.
Why is vitamin C so important for collagen?
This is the benefit that gets far less attention, and arguably the most important one. The skin needs vitamin C to form and stabilise collagen, the protein that gives skin its strength and structure.
Brightness is the result people see first. Structural support is the reason vitamin C has such a long standing place in dermatology.
What makes The Skin Diary Pro Helix C different?
The Skin Diary Pro Helix C Collagen Peptide Brightening Serum is the brand's first ever vitamin C serum, now at the Institute of Dermatologists. Developed by the consultant dermatologists behind Night Repair Therapy, it was designed to take vitamin C beyond its traditional protective role.
As The Skin Diary co-founder Dr Clare Kiely puts it, “We started with the biology of ageing skin.” The result is a patent pending complex of three actives, each chosen to work on a different pathway behind visible ageing:
- 15% THDA vitamin C: a stable, oil soluble form of vitamin C that delivers powerful brightening and antioxidant protection, formulated at a neutral pH so it suits sensitive skin.
- 0.5% acetyl zingerone: a broad acting antioxidant that helps optimise vitamin C and helps defend against collagen breakdown.
- 4.5% collagen signalling peptides: a dual peptide complex that supports collagen and the extracellular matrix, the network that keeps skin firm and supple.
The choice of THDA matters. Because it stays stable without needing a highly acidic base, Pro Helix C can deliver a meaningful 15% concentration in a milky, comfortable serum that sensitive skin can use every day.
What results can you expect from Pro Helix C?
The formula has been tested at both the surface of the skin and the cellular level. In clinical testing, 94% of participants showed brighter skin within seven days,¹ and 84% showed a visible reduction in fine lines and wrinkles at eight weeks.²
Below the surface, an independent, double blind, vehicle controlled skin biopsy study at the University of Manchester found a statistically significant increase in fibrillin in photoaged skin.⁴ Fibrillin is the scaffold the skin's elastic fibres are built on, and supporting it is key to skin that looks and feels firmer over time.
Perhaps the most telling result of all: 73% of testers said they would switch from their current vitamin C product.³ It is fragrance free, non comedogenic and dermatologically tested on sensitive skin.
How should you use vitamin C in your routine?
Morning is the ideal time for vitamin C, when its antioxidant role is most useful ahead of a day of UV and pollution exposure. A simple, effective morning routine looks like this:
- Cleanse, then apply 1 to 2 pumps of The Skin Diary Pro Helix C to dry skin, over the face and neck.
- Moisturise with EltaMD AM Restore, a lightweight, fragrance free moisturiser with hyaluronic acid.
- Protect with EltaMD UV Clear SPF 46, a calming sunscreen with niacinamide that suits sensitive skin. For a sheer tint and added antioxidants, choose EltaMD UV AOX Elements SPF 50.
Vitamin C and sunscreen work best as a team. Sunscreen reduces the UV that reaches your skin, while vitamin C helps manage the oxidative stress that still occurs.
In the evening, The Skin Diary Night Repair Therapy is the natural partner to Pro Helix C. Together they make a complete morning and night routine from the same dermatologist team.
Can you use vitamin C with retinol?
Yes, and it is one of the most common questions put to Professor Nicola Ralph on Ask ID. Her answer is that the real question is how and when. Keep vitamin C in the morning and your retinoid in the evening, and introduce new actives one at a time rather than starting everything at once.
If you are new to retinoids, start every two to three nights and build up to nightly as your skin adjusts.
“Slow, consistent use always wins,” says Professor Nicola Ralph.
Shop The Skin Diary Pro Helix C
The Skin Diary Pro Helix C is available now at the Institute of Dermatologists. Vitamin C has always been one of skincare's most valuable ingredients. Pro Helix C is what happens when dermatologists set out to make it work harder.
Frequently asked questions
What does a vitamin C serum do?
A vitamin C serum provides antioxidant protection against everyday environmental stress, helps brighten and even out skin tone, and supports the skin's natural collagen production.
Is vitamin C suitable for sensitive skin?
Yes, when it is the right form. Stabilised forms such as THDA can be formulated at a neutral pH, which makes them well suited to sensitive skin. The Skin Diary Pro Helix C is pH neutral and dermatologically tested on sensitive skin. As with any new product, patch test first.
Is vitamin C better in the morning or at night?
Morning is the most common recommendation, because vitamin C's antioxidant role is most useful during the day. It also leaves the evening free for a retinoid.
How long does vitamin C take to work?
Brightness can be visible within days. In clinical testing of The Skin Diary Pro Helix C, 94% of participants showed brighter skin within seven days.¹ Changes in fine lines build over time: 84% showed a visible reduction at eight weeks.² Consistent daily use matters.
Is a higher percentage of vitamin C always better?
Not necessarily. The form of vitamin C, how well it has been stabilised and the formula around it all matter as much as the number on the bottle. Pro Helix C pairs a stable 15% THDA vitamin C with complementary antioxidants and peptides.
Does vitamin C replace sunscreen?
No. Vitamin C supports the skin's antioxidant defences, but it does not block UV. A broad spectrum SPF every morning is still essential.
Can I use vitamin C with niacinamide?
Yes. Modern formulas use them together without issue, which is why vitamin C pairs well with a niacinamide sunscreen like EltaMD UV Clear.
¹ Independent instrumental clinical study, ADSL Ref. 41051, 32 participants, 28 days.
² Independent instrumental clinical study, ADSL Ref. 41053, 32 participants, 56 days.
³ Consumer perception study, ADSL Ref. 41054, 45 participants, 4 weeks.
⁴ University of Manchester, Manchester Patch Test Assay, in vivo skin biopsy study, double blind, vehicle controlled. Data on file, The Skin Diary.
