Highly stable, fast-absorbing and non-irritating, this advanced form of Vitamin C provides superior protection against oxidative damage from UV and pollution. Because it is an oil-soluble lipid, Tetrahexyldecyl Ascorbate (THDA) is able to penetrate deeper into the skin than traditional forms, delivering tangible benefits where they matter most.
What is Tetrahexyldecyl Ascorbate?
Vitamin C is widely recognised as the gold standard for brightening the complexion and restoring skin health. However, its most common form - L-ascorbic acid - is notoriously difficult to use. It is unstable and vulnerable to light and air, meaning it often oxidises and renders itself inactive before you finish the bottle.
That is why we use Tetrahexyldecyl Ascorbate (THDA). It is a stable, oil-soluble precursor to Vitamin C that solves the issues of traditional water-based serums.
Unlike L-ascorbic acid, THDA does not degrade immediately upon contact with air. It will not oxidise or turn that tell-tale orange/brown colour in the bottle after just a few uses. This stability means you can use every last drop with confidence that it is just as potent as the day you opened it. It also explains why we are able to house it in clear glass bottles to showcase the purity of the formula.
Furthermore, it is far gentler. While L-ascorbic acid requires a very low (acidic) pH to work - which often leads to stinging and redness - THDA is effective at a neutral pH. This makes it a non-irritating alternative that is perfectly suited for sensitive skin.
Why we pair it with Bakuchiol
Since THDA is oil-soluble, it integrates seamlessly into a barrier-supportive lipid routine. To maximise results, we pair it with Bakuchiol. This powerful antioxidant is a natural alternative to retinol that complements the brightening effects of Vitamin C while enhancing the stability of the overall formula.
We suspend these actives in a blend of melon and broccoli seed oils. These carriers are chosen for their lightweight profile. They absorb almost instantly, ensuring the treatment nourishes the skin while it corrects, without leaving a heavy or greasy residue.
What are the Benefits of Tetrahexyldecyl Ascorbate?
Fights free radicals. THDA reduces and suppresses damage caused by UVB and UVA light, acting as a second line of defence alongside your daily sunscreen. It supplements the body's natural reaction to free radicals and helps shield against oxidative stress. In doing so, it addresses the most common causes of premature ageing and environmental damage.
Improves skin tone. Research shows that THDA inhibits melanogenesis, the process responsible for producing pigment in the skin. This means it can help promote a more even complexion, leading to a visible reduction in age spots and hyperpigmentation. It is ideal for brightening dull skin and regenerating overall appearance.
Revitalises skin texture. THDA has been shown to boost collagen production, with some studies suggesting it may promote up to 50% more collagen than other forms of Vitamin C. This increase helps restore elasticity and firmness, leading to a healthy, rejuvenated texture. It is also excellent for blemish-prone skin, as it minimises redness from inflammation and helps fade old scarring.
How to Use Tetrahexyldecyl Ascorbate
In an oil-based formula like our Vitamin C + Bakuchiol Serum, THDA functions best when applied after lighter, water-based hydrating serums but before (or mixed with) your moisturiser.
Because THDA provides exceptional protection against oxidative damage, your skin will benefit most when using it as part of your morning routine. Always complete your regimen with daily sun protection as the final layer.
This article was originally written by Bryanna Martonis PhD, an ethical content creator and beauty awards judge. It has since been updated by Gabrielle Richens, a veteran model-turned-NVQ-qualified skin therapist, and an online skin coach.
