Foundation

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.

While tea tree oil is a pretty well established anti-acne ingredient, manuka has more of a "might be useful" status for problem skin. Its strong suit is treating fungal infections such as athlete's foot, nail bed infections or foot odor. Other than that, manuka can help to relax muscles (useful for treating muscle and joint pain) and also has some antioxidant activity.

Regarding skincare and tea tree oil, its most well-known effect is probably being a well established anti-acne ingredient. Multiple studies confirm that TTO is effective against the evil acne-causing bacteria called P. acnes and the effectiveness of 5% TTO gel is comparable to the gold standard anti-acne treatment, 5% Benzoyl Peroxide lotion. You need to be a bit more patient with TTO, though, as its effects come slower but also with fewer side effects.

Regarding TTO and sensitive skin, we say that you should be careful. Even if your skin is not sensitive you should never put undiluted TTO on your skin. Luckily, it contains only very small amounts of the common allergens (such as limonene), but irritant and allergic reactions still happen, especially by oxidation products that occur in older or not properly stored oil.  So if you have some pure TTO at home, know that storage matters, keep it in a cool, dry, dark place and use it up in a reasonable amount of time.

Overall, we do not often give a goodie status to essential oils, but we feel that TTO's unique antibacterial and anti-acne properties with its minimal allergen content warrant an exception. If your skin is acne-prone, TTO is something to experiment with.

Anyway, it doesn't matter if it reflects or absorbs, Titanium Dioxide is a pretty awesome sunscreen agent for two main reasons: it gives a nice broad spectrum coverage and it's highly stable. Its protection is very good between 290 - 350 nm (UVB and UVA II range), and less good at 350-400 nm (UVA I) range. Regular sized Titanium Dioxide also has a great safety profile, it's non-irritating and is pretty much free from any health concerns (like estrogenic effect worries with some chemical filters).

The disadvantage of Titanium Dioxide is that it's not cosmetically elegant, meaning it's a white, "unspreadable" mess. Sunscreens containing Titanium Dioxide are often hard to spread on the skin and they leave a disturbing whitish tint. The cosmetic industry is, of course, really trying to solve this problem and the best solution so far is using nanoparticles. The itsy-bitsy Nano-sized particles improve both spreadability and reduce the whitish tint a lot, but unfortunately, it also introduces new health concerns. 

The main concern with nanoparticles is that they are so tiny that they are absorbed into the skin more than we want them (ideally sunscreen should remain on the surface of the skin). Once absorbed they might form unwanted complexes with proteins and they might promote the formation of evil free radicals. But do not panic, these are concerns under investigation. A 2009 review article about the safety of nanoparticles summarizes this, "to date, in-vivo and in-vitro studies have not demonstrated percutaneous penetration of nanosized particles in titanium dioxide and zinc oxide sunscreens". The English translation is, so far it looks like sunscreens with nanoparticles do stay on the surface of the skin where they should be.  

All in all, Titanium Dioxide is a famous sunscreen agent and for good reason, it gives broad spectrum UV protection (best at UVB and UVA II), it's highly stable, and it has a good safety profile. It's definitely one of the best UV-filter agents we have today, especially in the US where new-generation Tinosorb filters are not (yet) approved. 

The first main difference is that while TiO2 gives a nice broad spectrum protection, Zinc Oxide has an even nicer and even broader spectrum protection. It protects against UVB, UVA II, and UVA I almost uniformly, and is considered to be the broadest range sunscreen available today. 

It's also highly stable and non-irritating. So much so that Zinc Oxide also counts as a skin protectant and anti-irritant. It's also often used to treat skin irritations such as diaper rash.

As for the disadvantages, Zinc Oxide is also not cosmetically elegant. It leaves a disturbing whitish tint on the skin, although, according to a 2000 research paper by Dr. Pinnell, it's slightly less white than TiO2. Still, it's white and disturbing enough to use Zinc Oxide nanoparticles more and more often. 

We wrote more about nanoparticles and the concerns around them here, but the gist is that if nanoparticles were absorbed into the skin that would be a reason for legitimate health concerns. But luckily, so far research shows that sunscreen nanoparticles are not absorbed but remain on the surface of the skin or in the uppermost (dead) layer of the skin. This seems to be true even if the skin is damaged, for example, sunburnt. 

All in all, if you've found a Zinc Oxide sunscreen that you are happy to use every single day, that's fantastic and we suggest you stick with it. It's definitely one of the best, or probably even the best option out there for sun protection available worldwide.