August 20, 2020 3 min read

Can a sunscreen be natural?

There are numerous products on the market that wear the natural badge and make a range of claims. For those of us who desire natural products, a natural sunscreen sounds like a great proposition. Let’s check the facts.

First, be aware that only a limited number of UV filters have been approved by regulatory authorities to be used to formulate sunscreens. Any cosmetic product claiming activity from other non-approved ingredients to achieve sun protection is, literally, playing with fire.

These approved UV filters can be split into 2 chemical categories: organic chemistry (organic meaning carbon-based); or inorganic chemistry (mineral-based). The next time you buy an “organic” product, "organic" may just mean “full of carbons”.

Most of the approved UV filters fall into the organic class: they have been invented by scientists. Therefore, a natural sunscreen cannot exist.

Two inorganic, mineral-based UV filters are approved for sunscreens: Titanium Dioxide and Zinc Oxide. The former is a strong UVB absorber crafted by scientists and therefore is not natural. The latter is a white mineral with UV reflecting properties across a large range of UV rays as well as a mild antimicrobial and anti-inflammatory properties. Zinc oxide is used in many applications, such as baby nappy rash creams.

Although zinc oxide is naturally occurring under a rare crystal form (known as zincite), that natural form is not usable for modern sunscreens.

The zinc oxide used as UV filter in sunscreens is produced in chemical plants using zinc chemicals as raw materials and is no more and no less natural than its organic cousins.

Despite its synthetic nature, zinc oxide is a very interesting chemical for sun protection as explained below.

Physics Reminder

A white paint will mostly reflect the visible light and its UV components, and that is the principle of the white zinc paste that we Australians apply on the face. The UV protection is provided by a physical reflection of all the light, including the UV rays.

Most people, however, don’t like to have a white paint on their skin, and scientists developed transparent, nano-sized or nano-structured zinc oxide that can be used in commercially-acceptable sun protection products.

These nano-engineered transparent zinc oxide particles act more like typical organic UV filters, by diffusing and absorbing the UV rays. Physical (reflecting) is replaced by chemical (absorbing).

The benefits of Zinc Oxide:

  1. Inert: zinc oxide is not degraded by UV rays and its efficacy remains constant during UV exposure
  2. Big enough: although a nano-sized particle can seem as tiny, it is still much larger than the older organic (carbon-based) UV filters used in most sunscreens. It has been scientifically proven that some of these organic UV filters can be absorbed by the skin because they’re really small when zinc oxide is just too big to go through the skin. Here, nano means bigger.
  3. Exceptional broad UV absorption: Zinc oxide has an excellent UV absorption profile and can provide strong broad-spectrum protection alone.
  4. Mild antimicrobial effect: a zinc-based sunscreen will help cure your skin of all the little irritations it may face.

Zinc is not a magic “silver bullet” though, and has a few intrinsic limitations worth remembering.

  1. Zinc oxide is not a strong UV absorber in the UVB arena; the usual SPF ratio is 1.5 unit of SPF per gram of zinc oxide, which means a 22% zinc oxide sun cream will generally achieve SPF30.
  2. The more zinc oxide in a formulation, the more “pasty” the sunscreen becomes, the harder it is to apply consistently and correctly.
  3. Zinc oxide is dense and may sediment (settle) in fluid formulations. Most sunscreens using zinc will be thick enough for the zinc oxide to remain persistently dispersed in the formula.

In summary, despite its synthetic nature, we believe Zinc Oxide is a great UV filter for those with sensitive skin, or seeking an excellent UVA protection, or concerned by the penetration of some organic UV filters into the skin.