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I read an old post where Susanne (I think) mentioned mixing hyaluronic acid with emu oil. I wonder if it would work to mix ascorbic acid with these two? Would mixing the emu with hyaluronic acid make the ha penetrate deeper into the skin? Any ideas? Terri or D or anyone? (Terri and D, I think you are becoming the new "gurus"!)
Well, hyaluronic acid has too high a molecular wt to absorb into the skin...even the low molecular wt one. It is a very good moisturizer just because of the film it forms on the surface...so a good ingredient, but not to really increase HA levels IN the skin.
Abstract: Human skin has unique properties of which functioning as a physicochemical barrier is one of the most apparent. The human integument is able to resist the penetration of many molecules. However, especially smaller molecules can surpass transcutaneously. They are able to go by the corneal layer, which is thought to form the main deterrent. We argue that the molecular weight (MW) of a compound must be under 500 Dalton to allow skin absorption. Larger molecules cannot pass the corneal layer. Arguments for this "500 Dalton rule" are; 1) virtually all common contact allergens are under 500 Dalton, larger molecules are not known as contact sensitizers. They cannot penetrate and thus cannot act as allergens in man; 2) the most commonly used pharmacological agents applied in topical dermatotherapy are all under 500 Dalton; 3) all known topical drugs used in transdermal drug-delivery systems are under 500 Dalton. In addition, clinical experience with topical agents such as cyclosporine, tacrolimus and ascomycins gives further arguments for the reality of the 500 Dalton rule. For pharmaceutical development purposes, it seems logical to restrict the development of new innovative compounds to a MW of under 500 Dalton, when topical dermatological therapy or percutaneous systemic therapy or vaccination is the objective.
Blah, blah, blah...things need to be very very small to get in. There are lots of studies on molecular wt and topical absorption so I posted a short abstract of one. If you are interested google for more info. Some things maybe as large as 5000 daltons can get in in small amounts, but it depends on the vehicle, condition of the stratum corneum, etc.
Retin a has a wt of about 300, niacinamide 122, vitamin c 176 etc. These are all scientifically proven to absorb when applied topically. When I am thinking of a "new" ingredient I always google for the molecular wt. SLMW HA is still 50,000 daltons. BIG.
HA and Vitamin c are both water soluble as D said, so mixing them with an oil without an emulsifier won't work. And you can't mix up a batch of vitamin c that will stay stable for longer than a week in aqueous solution and that's keeping it in the fridge away from a light source.
If you want to mix the c with the hyaluronic acid and put it on your skin, then put the emu oil over it to kind of lock in the moisture, that might work fairly well.
I've read on on several sites that less than perfect skin (skin that has been ravaged by age and sun damage/free radicals) is more permeable than younger skin-it is more penetrable due to its state of imperfection (old vs young skin).
Thank you Gurus! Question: Any idea how I would figure out the molecular weight of the New Face Solution (estriol) cream? If it has a lower molecular weight, and therefore penetrates more readily into the skin, would it also be absorbed into the system possibly? It seems like it would, but just wanted to double check with my gurus. If so, would applying hyaluronic acid before applying the cream possibly make it less apt to be absorbed into the system, yet still allow the skin benefits? Thanks for any thoughts on this.
Editing to say I found the molecular weight for estriol crystals is 288.39, and glycerine is 92.09. (Glycerin is the third highest ingredient.) Does anyone know how to figure the molecular weight of water? I tried googling but only got complicated formulas for water.
Is this line of thinking even making sense? That there would be less chance of any estriol being absorbed in one's system if it were applied in a higher molecular weight carrier? I believe the estriol does improve the skin, but am concerned about it being absorbed into the system.
Here are the ingredients for the new face solution: (Would it make sense to either mix it with HA, or apply HA before applying the cream? HA is an ingredient in the cream already also.)
I emailed you an answer, but want to clarify here for anyone looking at the post later.
I didn't mean to imply that the size of the molecule was the determining factor of absorption. Only that if a molecule is too big I wouldn't expect it to be absorbed at all. There are so many other factors (that I won't go into, and admittedly don't understand completely) having to do with the bioactivity of any substance.
Just because the carrier is a high molecular wt does not mean it will block absorption. HA creates a permeable viscoelastic layer, meaning things can get through it.
The wt of water is 18 daltons per molecule.
Don't get too "sciency" in your thinking. I just look up the weight to see if an "active" is possibly completely useless before researching it more. Lots of peer reviewed studies are the gold standard, and we only have those for Retin a and vitamin C. Niacinamide has a couple, but hopefully will have more in the future. Plus there are many substances that are protective and do other good things for our skin without being absorbed.
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