Safe Sunscreen: What You Need to Know About Chemical Absorbers vs Physical Barriers

Updated 2 November 2017

There's something about sunshine that makes you happy, isn't there? Coming out of a really cold winter in Victoria this year, it's lovely to finally be able to sit out in the sunshine, feel the warmth on your face and defrost the extremities. And before long, our thoughts will turn to how hot it is, and how we really need to put on some sunscreen and a hat before we go outside. And that's how we've ended up on today's topic: absorbers vs barriers. While I've been updating the Sunscreen Cheat Sheet, I've been thinking about ingredients in sunscreens, and thought it was time to discuss active ingredients and how they work.

In Australia, all sunscreens must be registered by the TGA. There are a number of permitted active ingredients that are used in sunscreens. The active ingredients are the ingredients that protect you from the sun. The inactive ingredients are things like moisturisers, fragrances and preservatives.

Absorbers (Chemical) vs Barriers (Physical)

Active ingredients in sunscreens can be divided into two groups: absorbers and barriers. There are chemical absorbers, and then there are physical barriers or blockers. Physical barriers tend to be minerals. You may see them called mineral sunscreens because of this. The most common physical blockers are Titanium Dioxide and Zinc Oxide. Barrier, mineral or physical sunscreen ingredients work by putting a layer on your skin and physically deflecting or scattering UV radiation. You may also hear them called sunblocks (although manufacturers in Australia aren't allowed to call them this, as they don't block all the radiation).

Physical blockers protect against both UVA and UVB radiation. Chemical sunscreens work by absorbing UVA and UVB rays. Some absorb UVA radiation, some absorb UVB radiation, and some absorb both. Some of the most common chemical absorbers are:

• Avobenzone
• Oxybenzone
• Octylcrylene
• Octinoxate
• Octisalate
• Homosalate

So that you can get full UVA and UVB protection, absorbers are often combined with another absorber, or with titanium dioxide or zinc oxide.

Which are best - absorbers or blockers?

The important thing with sunscreen is that it protects your skin. Both zinc oxide and titanium dioxide are physical blockers, and offer full spectrum protection, so they're good choices. Zinc oxide is the safest, as there are very few health concerns with it. It's soothing, and is used as an anti-irritant, so it's ideal for people with sensitive skin and for children. Chemical absorbers seem to have a few issues, however. Many are skin irritants, and some have been linked to hormone disruption. And while links to hormonal issues may not yet be proven, there can be a more immediate problem. This is one that I, and one of my sons know too well:

"Photopatch testing shows sunscreen chemical absorbers to be a common cause of photoallergic contact dermatitis."

In other words, some sunscreen chemical absorbers will cause an allergic reaction once you go out in the sun. When my eldest was very young, he would just refuse to have sunscreen applied, because he knew that he would have inflamed and irritated skin at the end of the day. Sunscreen allergies can also be caused by the inactive ingredients, like the perfumes and preservatives used. One of the problems with buying sunscreens is that manufacturers don't have to disclose the full ingredients lists, so it can be hard to tell what else in the product you might be having a reaction to. So as far as both chemical safety, and avoiding irritants goes, it seems that physical blockers are the way to go. But wait. There's more. As the infomercials used to say.

Nanoparticles and physical blockers

The problem with blockers is that they don't go on clear. Remember brightly coloured zinc creams from when you were a kid? They were a thick, opaque layer thanks to the micro-sized particles that formed the barrier on your skin. Most people don't want a visibly white layer on their skin, and so although they're very effective, consumers don't want to use them. The mineral particles can be micronized (made smaller) so that they go on clearer. In fact, they can be micronized to nano size, which is when they become nanoparticles. The TGA says that nanoparticles aren't an issue, and doesn't require them to be listed on sunscreen packaging. This is a problem if you're concerned about nanoparticles - it's can be very hard to find out whether or not your sunscreen contains them. For me, I grew up in Queensland. I know the sun's rays are harmful and definitely cause cancer. Me and my two brothers have all had basal cell carcinomas removed, thanks to a childhood in the Queensland sun. (It was a very happy childhood, I must point out!)

The link between nanoparticles and endocrine disrupters is less clear. My money is on the certainty - always use sunscreen, and if you can't get a non-nano blocker, and can only get a sunscreen with a chemical absorber - go with that for the day. It's worth stocking up on a good, zinc based natural sunscreen with a high SPF for the best sun safety. And of course, stay out of the sun during the hottest part of the day, wear a hat, cover up, and stay in the shade as much as possible.