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Vitamin C is one of the most important things you can put on your skin.
The vitamin C everyone knows is not the one I trust most anymore.
And the form most people still chase may be the very one holding them back.
In this video, I sit down with a skincare PhD who no longer recommends the classic form so many people swear by. We get into the stability problem, the low-pH trap, why irritation is often mistaken for results, and the newer form that may make a lot more sense for real-world skin.
If your skin has ever felt stingy, reactive, tight, or just not better despite “doing all the right things,” this may explain why.
There is a reason more formulators are quietly shifting.
And most consumers still have no idea.
Watch this before you buy your next vitamin C.
—————Studies———-
Pinnell SR, et al. Dermatol Surg. 2001. Topical L-ascorbic acid absorption was highest at very low pH, below 3.5, helping explain why it can work but also why it can be irritating and hard to tolerate long term.
Crous C, Granger C, Luebberding S. Skin Health Dis. 2024. Review: L-ascorbic acid remains effective, but instability and irritation are major drawbacks. More stable derivatives were developed to improve delivery and tolerability.
Swindell WR, et al. J Cosmet Dermatol. 2021. Tetrahexyldecyl ascorbate is a lipophilic vitamin C derivative designed to improve penetration and stability, though formulation quality still matters.
Kazemeini S, et al. 2025 clinical review. Many topical vitamin C products now use derivatives such as tetrahexyldecyl ascorbate because they are more stable and can be converted in skin to active ascorbic acid.
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FTC: Some links included in this description might be affiliate links. If you purchase a product through one of them, I will receive a commission (at no additional cost to you). I truly appreciate your support of my channel. Thank you for watching! Video is not sponsored. DISCLAIMER: This video does not contain any medical or health related diagnosis or treatment advice. Content provided on this YouTube Channel is for informational purposes only. For any medical or health related advice, please consult with a physician or other healthcare professionals. Further, information about specific products or treatments within this video are not to diagnose, treat, cure or prevent disease.
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0:00 The truth about vitamin C
0:26 Why the old favorite may be outdated
1:12 The serum problem most people miss
2:03 Why that sting is not a flex
3:01 The pH issue changing your skin barrier
4:06 The smarter delivery system
5:08 Why THD is showing up everywhere
6:10 How to choose vitamin C without getting fooled
source
On Sale Now: https://store.rajanimd.com/collections/vitc-special
This was not a scientific discussion. A lot of claims, no study discussed (mentioned, not discussed). Petry dish experiments were mentioned as if that's enough proof for a product efficiency (it's just the first step). Stability and penetration is not the only thing that needs to be tested, ascorbic acid works in many different problems, so each derivative needs to be tested for each one of them. Not to mentioned, conflict of interest needs to be taken into account, and studies coming from a brand that sells said ingredient is always something to be cautious about.
If anyone is interested in seing an actually Study Analysis, check out "Chemist Confessions" episode about THD
There are MANY OTHER antioxidants to take advantage of besides Vit C.
I use skinbetter’s alto advanced defense and repair formula. It has THD ascorbic in it. I do get a little rash if I use it too often though.
Dr Rajani, do you like tetraisopulmitate? Will be grateful if you give us light on this please.🙏🏽
Doctor, your skin looks great. May I ask how old you are?? I only want to know how old you are to see if I'm shocked at how well you're preserving yourself. I mean this in a good way of course.
Dang , he looks good!! 🇬🇧 . I also stoped using them vit C’s
Dr Rajani I've been recommended first quantum rf and then radiesse for lower face rejuvenation. What do you think of this approach or do you have a video that talks about these? Should I start with at home rf device first and see what I can achieve? Do you have a distributor in Canada? The tariffs right now are craaaaazy.
I love my revision c complex 30%. I panicked when I saw this title but was so relieved when I heard her say she's from revision.
Many of us have known THD (which is a form of Vit C) is more stable and very beneficial. It’s used in a lot of great products (like AnteageMD). I top up my morning regimen with a layer of Vit C/LAA for surface glow
meh. thd is not great. it simply doesn't work.
A PhD in health care😂
Hello DR Rajani ❤once again you have opened our eyes , to the truth . we are very grateful for your support , and your service to us all . We Thankyou for all your , hard work and dedication in this matter.
Thank you Dr Rajani love from Australia
This video makes me so happy because I get revision brand from a place I go! And I of course buy your collagen, my fav. I have that exact same vit C you showed and im on my first 30 days.
As a metabolic byproduct, vitamin C converts into oxalate, which can form calcium-oxalate kidney stones. Over 500 daily is dangerous.
Been using Florence C bio cosmesi, Siero Viso bio con Vit C Professional Facial Serum. 6o ml. Made in Italy.
Thank you Dr. Great information
Jen R. N. 🎉
THD has big molecular weight / Dalton rule. Any link of data to read?
Hey doc I use the ordinarys ascorbyl tetraisopalmitate solution 20% in vit f. Is it a good one
This is true, but a little known skin cancer cure is a 30% w/v ascorbic acid in dmso. Apply twice daily for up to 12 weeks. This works, but must be remixed/made every week or so because dmso absorbs moisture and the ascorbic acid hydrolyzes. Vitamin c is sooooo good. It is even given IV for great results.
Of course his products only….!. Very funny
I would never use Vit C. It's photosensative. I was so surprised that it was ever pushed in skincare.
Great interview
How about 3-O-Ethyl Ascorbic Acid? it is also used in products for the same reasons described in this video.
Tried it and loved it, but developed an allergic reaction after a few weeks.
I had started high levels of vitD and several other supplements 2 weeks ago . I also started using plain Greek yogart adding tumeric and using as a face mask several times this week. Wow it really made a difference. I have a glow and no flaky skin. Still have wrinkles though
It always irritated my skin too much so I gave up. And I’m someone who responds will to tazarac which most people find very irritating.
I adore Vitamin C Glow Potion (Advanced THD Ascorbate with Turmeric & Tomato Oil) from Australian natural skincare brand, The Jojoba Company. It is a dream for my menopausal skin & it soothes the occasional dryness I get form using tretinoin. I have been using it for years & highly recommend it!
She looks like the goth girl from Romy and Michele's high school reunion 😂
Is this ingredient for sensitive skin? I have resilient skin and have used Timeless brand 20%z Ive never had a batch that turns yellow color with their pump dispenser bottles.
I need to get started on topical vitamin c 🍊 I’ve been good with consuming it throughout the years and I do feel like it has helped my skin ✨