juicy chemistry

Blood Orange And Rose Hip Lip Balm

While it is very unlikely (and this is true for pretty much every ingredient), cases of reactions to castor oil have been reported, so if your skin is sensitive, it never hurts to patch test. 

In skincare two major types of rosehip oil are used:

1. Rosa Rubiginosa that is a synonym for Rosa Eglanteria and for Rosa Mosqueta. We will call it RR from now on. 

2. Rosa Canina, or RC

The oil content and composition of RR and RC is similar, but there are some differences: RR contains 8% of oil, while RC contains a bit more, 10%. However, the quality of RR oil seems to be a bit better: it contains 78% essential unsaturated fatty acids while RC contains only 71%. Also, the linoleic-oleic ratio of RR is better (3.3 vs 2.5) that might be important if your skin is acne-prone (as linoleic acid is good for acne and oleic is not). 

There is one more important thing to mention: RR oil is famous for containing the miracle active, tretinoin. Though Wikipedia puts RR and RC oil under the same article called as Rose hip seed oil, the referenced research about tretinoin content examines only Rosa Rubiginosa. We looked for a research paper explicitly stating that Rosa Canina also contains tretinoin, but could not find one, so we can neither deny nor confirm it. What we could find is a paper mentioning the tocopherols (vitamin E) and carotenoids (pro-vitamin A) content of Rosa Canina oil that gives it some nice antioxidant properties.

All in all, it is a great emollient plant oil with great fatty acids beneficial for any skin type. 

So what the heck is a wax ester and why is that important anyway? Well, to understand what a wax ester is, you first have to know that oils are chemically triglycerides: one glycerin + three fatty acids attached to it. The fatty acids attached to the glycerin vary and thus we have many kinds of oils, but they are all triglycerides. Mother Nature created triglycerides to be easily hydrolyzed (be broken down to a glycerin + 3 fatty acid molecules) and oxidized (the fatty acid is broken down into small parts) - this happens basically when we eat fats or oils and our body generates energy from it.

Mother Nature also created wax esters but for a totally different purpose. Chemically, a wax ester is a fatty acid + a fatty alcohol, one long molecule. Wax esters are on the outer surface of several plant leaves to give them environmental protection. 25-30% of human sebum is also wax esters to give us people environmental protection. 

So being a wax ester results in a couple of unique properties: First, jojoba oil is extremely stable. Like crazy stable. Even if you heat it to 370 C (698 F) for 96 hours, it does not budge. (Many plant oils tend to go off pretty quickly). If you have some pure jojoba oil at home, you should be fine using it for years. 

Second, jojoba oil is the most similar to human sebum (both being wax esters), and the two are completely miscible. Acne.org has this not fully proven theory that thanks to this, jojoba might be able to "trick" the skin into thinking it has already produced enough sebum, so it might have "skin balancing" properties for oily skin.

Third, jojoba oil moisturizes the skin through a unique dual action: on the one hand, it mixes with sebum and forms a thin, non-greasy, semi-occlusive layer; on the other hand, it absorbs into the skin through pores and hair follicles then diffuses into the intercellular spaces of the outer layer of the skin to make it soft and supple.

On balance, the point is this: in contrast to real plant oils, wax esters were designed by Mother Nature to stay on the surface and form a protective, moisturizing barrier and jojoba oil being a wax ester is uniquely excellent at doing that.