Beauty related chemistry behind hyaluronic acid

I was inspired to start my science infused beauty and fitness blog when one of my favourite vloggers confused hyaluronic acid with hydrochloric acid. I have come across many situations like this one where a lot of us, even myself, get hyped up about ingredients and products without any scientific understanding and blindly follow the current trends. However, the difference in knowledge can be staggering! Scarily enough, hydrochloric acid can permanently burn your face, whereas hyaluronic acid has been known as “the fountain of youth” molecule. So it is needless to say that some information and understanding can go a long way. As a result, here’s a hopefully informative entry on a little bit about the chemistry behind hyaluronic acid. I hope you find this interesting, please like, subscribe and share.


From a chemists perspective, hyaluronic acid is a polymer (a long molecule consisting of repeating units, see picture below) so it is essentially, one molecule, a fragment, that is repeated many, many times a bit like many identical in colour, size and shape Legos placed on top of each other. But how many times, might you ask? Well that actually depends on the chemist’s recipe or the source they are extracting it from.


The hyaluronic acid repeating unit


By definition, hyaluronic acid is a polymer with “n” repeating units so it is up to the beauty companies, to make this as long or short as they wish in order to achieve the physical and chemical properties they require. What I’m saying here is, a hyaluronic acid polymer is not a highly specifically defined entity (as opposed to any non-polymer molecules) and therefore, even though two different products might both claim to contain hyaluronic acid, they might not actually contain the exact same length or purity of molecule.


Why do we care? Well for two reasons. Molecules have chemical and physical properties depending on their structure and purity and therefore, the different structure, the different the properties and by extent the effects can also be potentially different. Additionally, this also means that, strictly speaking, just because two products both state that they contain hyaluronic acid this might not actually deem them directly comparable and so if one product doesn’t work for you, another might!


Polymers are synthesised, just like your Lego tower, by adding more and more pieces to the chain until you are happy. However, unlike you being able to control accurately how many Lego pieces you are going to make your tower of, molecules are much harder to control rising in a pool of very similar, but different in length, chains. Some chains might have 2 blocks less or 4 more etc. As a result, the stated length “n” is a number that represents an average in length, sizes. Depending on how accurate the synthetic and purification process is (or the source where the ingredient is extracted from) the average can be very small, meaning that the majority of the molecules have the desired length (which might be the the one that works best) or really high resulting in a pool of molecules of different length. You can imagine that cheaper synthetic procedures will, most of the time, induce less synthetic control and lower purification standards and therefore, will result in a pool of polymer molecules which might decrease the effectiveness of the compound.


Finally, let’s ask one more question. Does taking an ingredient orally (by ingestion) or topically (by absorption) make a difference? Absolutely! And a huge one actually! Some molecules might be broken down by digestion, when taken as a tablet and therefore taking them in this form might reduce their activity. On the other hand, some molecules might be too big or structurally not correct to be allowed to go through the skin’s membrane barrier resulting in only a small amount of them being absorbed or even nothing at all! As you can imagine, this would obviously also have an impact on the effectiveness of an ingredient and these are factors that we must also consider when talking about the effectiveness of an ingredient. Some companies use the promotional hype and scientific evidence of certain ingredients in let’s say, skin care, and although some of those ingredients might be perfectly legit, their action through skin absorption, might be very limited. Thankfully, hyaluronic acid, of the right size, can be absorbed by skin.


If you want to know if there is any scientific evidence behind the beauty claims of hyaluronic acid check out “Hyaluronic acid – The fountain of youth?” post.



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