The science behind sunscreen and SPF

Are sunscreens safe?

We know many Australians – whether mums and dads, young people, or seniors – have questions about sunscreen. 

Rest assured, decades of research and long-term studies of sunscreen use here in Australia have found no harmful effects of regular use. 

In other words, you can feel confident knowing sunscreens sold in Australia are safe to use and effective at preventing skin cancer. 

In fact, there is clear evidence that regular use of sunscreen helps prevent skin cancer. 

Sunscreens are regulated by the Therapeutic Goods Administration (TGA), which ensures the safety, quality and efficacy of products. 

The TGA has advised that sunscreens available to purchase in Australia are safe and effective to use, and Australians should continue using sunscreen as one of five forms of sun protection. 

How do sunscreens work?

The TGA does not allow sunscreens to use the term ‘sunblock’, because no sunscreen can block 100% of UV radiation.  

There are two main parts to all sunscreens – the active ingredients and the different bases they are mixed in to provide the large variety of available products, known as the emulsion. 

The active ingredients do the sun protection work and they work in two ways: 

1. “Physical” or “mineral” sunscreens contain active ingredients which primarily absorb, and also reflect, ultraviolet (UV) radiation which prevents it from reaching the skin They contain particles of minerals such as zinc oxide and titanium dioxide and may have a milky-white appearance when you apply them to your skin. 
2. “Chemical” sunscreens contain active ingredients which absorb UV radiation and convert it into heat energy, which is then released from the skin. They usually contain a mixture of synthetic chemicals and are usually invisible when you apply them to your skin. 

Typically, there’s more than one and often up to six or more active ingredients in most sunscreens.  

The emulsion is the lotion, milk, cream, oil, foam or gel – it’s what carries the active ingredient. It is usually made up of some combination of oil and water, plus other ingredients to help preserve the sunscreen so it lasts on the shelf or in your cupboard. 

Emulsion ingredients also help with water resistance, influence how the sunscreen feels and smells, and how well it binds to the skin. 

Both physical and chemical sunscreens can be broad-spectrum, water-resistant and both deliver effective protection. No sunscreen is completely waterproof, and all sunscreens become less effective after exposure to water.  

Are nanoparticles in sunscreens safe?

Nanoparticles are tiny particles that are so small you need a specialised microscope to see them. Some sunscreens use nanoparticles of the mineral ingredients zinc oxide and titanium dioxide.  

Nanotechnology has been safely used in sunscreens for many years. 

Research shows nanoparticles are safe when used as directed.  

In 2017, the Therapeutic Goods Administration (TGA) reviewed studies on the safety of nanoparticles in sunscreens. The evidence shows they don’t go deep into your skin. Even if a small amount does get through, it’s so tiny that it’s very unlikely to cause harm.