Vanicream

Vitamin C Serum

It's a really promising candidate (see below), but while reading all the goodness about it in a minute, do not forget that derivatives not only have to be absorbed into the skin but also have to be converted to pure vitamin C (ascorbic acid or AA) and the efficacy of the conversion is often unknown. In addition, vitamin C's three magic properties (antioxidant, collagen booster, skin brightener) are all properly proven in-vivo (on real people), but for the derivatives, it's mostly in-vitro studies or in the case of THDA, it's in-vitro and done by an ingredient supplier.

With this context in mind let's see what THDA might be able to do. First, it is stable (if pH < 5), easy to formulate, and a joy to work with for a cosmetic chemist.

Second, because it's oil-soluble, its skin penetration abilities seem to be great. So great in fact, that it surpasses the penetration of pure vitamin C threefold at the same concentration and it penetrates successfully into the deeper layers of the skin (that is usually important to do some anti-aging work). There is also in-vitro data showing that it converts to AA in the skin. 

Third, THDA seems to have all three magic abilities of pure vitamin C: it gives antioxidant protection from both UVB and UVA rays, it increases collagen synthesis (even more than AA) and it has a skin brightening effect by reducing melanogenesis by more than 80% in human melanoma cell cultures.

So this all sounds really great, but these are only in-vitro results at this point. We could find Tetrahexyldecyl Ascorbate mentioned only in one published in-vivo study that examined the anti-aging properties of a silicone formula containing 10% AA and 7% THDA. The authors theorized that the 10% AA is released slowly from the silicon delivery system and probably stays in the upper layer of the skin to give antioxidant benefits, while THDA penetrates more rapidly and deeply and gives some wrinkle-reducing benefits. The study was a small (10 patients), double-blind experiment, and the formula did show some measurable anti-aging results. However, it is hard to know how much pure vitamin C or THDA can be thanked.

Bottom line: a really promising, but not well-proven vitamin C derivative that can be worth a try especially if you like experimenting (but if you like the tried and true, pure vitamin C will be your best bet).

Other than that we can write about manufacturer-done in-vitro (in the lab, not on real people) studies that show Carnosine to have anti-glycation properties. Glycation is the not-so-nice process that happens when we bombard our body with too much sugar that results in damaged body proteins and eventually in more wrinkles.  

Also, a manufacturer done in vitro study shows that carnosine might have collagen-boosing magic power. However, the 2017 research paper also mentions that even though Carnosine is a small molecule, it is water soluble and does not penetrate the skin past the top layers so we have some doubt if the collagen-boosting works in real life. We could find one anti-aging study made on real people that mentions Carnosine, but it was combined with a bunch of other anti-aging actives so it is pretty much impossible to know what Carnosine did or did not. 

One last thing to mention is that there is also a manufacturer done clinical study (done on real people) that shows carnosine being effective against the damages caused by infrared (IR) radiation. (source)

Ok, so now we know what ceramides are, let's see what they do in our skin: research shows clearly that they play a super important role in keeping the skin barrier healthy and the skin hydrated. If ceramides in the skin are decreased, more water can evaporate from the skin and there is less water remaining in the skin. So ceramides form kind of a "water-proof" protecting layer and make sure that our skin remains nice and hydrated. 

Now the question is only this: If we put ceramides all over our face do they work as well as ceramides already naturally in our skin? Well, the answer is probably a no, but they do work to some extent. The BeautyBrains blog made a fantastic article about ceramides and they have listed a couple of examples about studies showing that ceramides - especially when used in certain ratios with cholesterol and fatty acids  - do hydrate the skin and can help to repair the skin barrier.

So far we were writing about ceramides in plural. It's because there are lots of different ceramides, a 2014 article writes that currently 12 base classes of ceramides are known with over 340 specific species. Chemically speaking, ceramides are the connection of a fatty acid and a sphingoid base and both parts can have different variations that result in the different types of ceramides. 

Our current one, Ceramide 1, or more recently called Ceramide EOP, was the first one that was identified in 1982 and it's a special snowflake. It contains the essential fatty acid, linoleic acid and has a unique structure. It's believed that ceramide 1 plays a "binding role" in the lipid layers of the extracellular matrix. Along with ceramides 4 and 7, they also play a vital role in epidermal integrity and serve as the main storage areas for linoleic acid (a fatty acid that's also very important for barrier repair).  

Oh, and one more thing: alkaline pH inhibits enzymes that help ceramide synthesis in our skin. So if you use a soap and you notice your skin is becoming dry, now you know why. 

It also occurs naturally in our body and is used as a food additive. As cosmetic chemist Colins writes it, "its safety really is beyond any doubt".

There is also some research showing that citric acid with regular use (think three months and 20% concentration) can help sun-damaged skin, increase skin thickness and some nice hydrating things called glycosaminoglycans in the skin. 

But according to a comparative study done in 1995, citric acid has less skin improving magic properties than glycolic or lactic acid. Probably that’s why citric acid is usually not used as an exfoliant but more as a helper ingredient in small amounts to adjust the pH of a formulation.