Not all vitamin C ingredients are created equally and what is now considered “the gold standard” is Tetrahexyldecyl Ascorabate, also known as THD Ascorbate.
So, let’s do a deep dive into this ingredient, shall we?
What is THD Ascorbate?
THD, or Tetrahexyldecyl Ascorbate, is an inactive form of vitamin C. What makes THD Ascorbate so uniquely different from other forms of vitamin C is that it’s an oil-soluble ester versus being water-soluble. When it’s oil-soluble, it means it won’t start to react and convert into L-ascorbic acid until it hits the oils in your skin, making it the most stable compared to other forms of vitamin C. Plus, since it’s solubilized by oil instead of water, it doesn’t require a low pH like the water-soluble versions do.
Why Choose THD Ascorbate Over Other Types of Vitamin C For My Face?
Have you ever gotten a stinging sensation from vitamin C products with Ascorbic Acid, Sodium Ascorbyl Phosphate and Ascorbyl Methylsilanol Pectinate? Yep, that is an indication of their low pH along with potentially the state of your skin’s barrier. While stinging from vitamin C with a low pH is par for the course, that doesn’t mean your skin appreciates the daily “no pain, no gain” assault that it gets exposed to in the quest for brighter skin. Your skin’s pH resides around 5.0 and many of the water-soluble acids can be a pH of 4.0 or even lower so that’s where the “ouch factor” comes from.
If your goal is to create a smoother, even-toned texture with less visible pores, there will be side effects that can compromise the skin barrier and cause irritation, but putting your skin in a state of increased sensitivity every single morning with the use of a low pH vitamin C serum? Nope. I am absolutely not a fan of that.
How Effective is THD Ascorbate for Reducing Brown Spots and Hyperpigmentation?
I was introduced to Tetrahexyldecyl Ascorbate last year while looking for better solutions for my clients struggling with hyperpigmentation from sun, hormones, and breakouts. Initially, I was looking at Hydroquinone to target pigmentation which is still known to be very effective, but during an online cosmetic chemistry class, I learned about THD’s promising effects on melanin production. Aside from it not being irritating, what stood out was its stability—it was effective down to the last drop, ensuring you can get the most out of the investment.
This sparked my journey with THD, and so I started to develop a serum using this ingredient. For those of you who don't know, I work with a lab and chemist (mom and daughter duo) in New Jersey to manufacture my products.
What Percentage of THD Ascorbate Is Effective?
It’s less about looking on the ingredient list (known as the INCI list) and more about the type of product that uses it. Because THD Ascorbate requires time to penetrate the skin, it’s best used in leave-on products. I don’t recommend it in products that rinse off the skin because there simply is no time for the THD to get to work. Also, THD requires much lower use levels than ascorbic acid, thanks to its supreme ability to penetrate into the skin. Oftentimes consumers like to see higher percentages of ingredients, but more is not always more! Skin doesn’t need as much THD as ascorbic acid to reap its benefits. For example, there is a study showing the collagen-boosting effects of THD at just 0.1%. For skin brightening, there are benefits seen as low as 0.5%.
How Often Should I Be Using A Vitamin C Serum?
The benefits of using a vitamin C serum is when it’s used daily as part of your morning routine. Not only does it help suppress melanin production but the use of all types of vitamin C helps to protect skin cells from environmental damage. It scavenges free radicals which are unstable molecules that lead to skin damage and accelerate skin aging. Free radicals are constantly coming at us from so many different sources, including UV light from the sun, ozone, smoke, and pollution (to name a few). All of these are also responsible for a natural depletion of vitamin C in our skin over time, which is why eating your vitamin C is also so important.
Bonus: Vitamin C helps prevent collagen breakdown and promotes healthier collagen production. First, it helps protect the collagen you already have by inhibiting a group of enzymes that break down collagen. Second, it aids in healthier collagen production since it’s a cofactor for two enzymes needed to build and cross-link collagen.
When In My Routine Should I Be Using A Vitamin C Serum?
Always in the morning. Here’s how I love to use it: after I’ve cleansed and my skin with Six Muses Cold Cream, I’ll use two pumps of Stellar C and gently press it into my skin with my fingertips, really letting it set into the skin for about a minute. This gives the powerhouse ingredients a moment to do their thing before I move on to my next step.
After that, I finish off with my favorite Astro Glow peptide eye cream and SPF, locking everything in and protecting my skin from those pesky free radicals. It’s a simple but super effective combo that leaves my skin feeling fresh, nourished, and ready to take on the day!
Also, I should mention, if you're looking for something even more natural, my Nourish and Glow oils are packed with vitamin C extracts like watermelon seed oil and rosehip- they will deliver brightness to the skin (but aren't as strong for fading spots). That said, all of my products are formulated without parabens, phthalates, sulfates, PEGS, mineral oils, artificial fragrances, and silicones. I'm always aiming for the EWG standard score of 1 with all of my products. They are also cruelty-free.
Stellar C will be available to purchase on July 1st, 2025. Mark your calendars!
