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What you need to know about sunscreen, according to experts

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21 December 2021|3 min read

Key points

  • There are two main types of active ingredients in sunscreens. They work by either absorbing or reflecting UV rays. 
  • Many people aren’t putting enough sunscreen on their skin – you should aim for a teaspoon for each body section. 
  • When used correctly, you should not be able to get a tan through your sunscreen. 
  • Talk to your dermatologist about the best options for sensitive and oily skin.

We all know that we need to wear sunscreen, right? It’s part of the five essential sun protection habits that SunSmart recommends. Sunscreen may also prevent premature signs of ageing. But what a lot of us don’t know is, how does sunscreen actually work? 

It turns out there are a LOT of commonly searched sunscreen related questions, so we spoke to dermatologist Dr Liz Dawes-Higgs to get some answers for you. 

Are you ready for a deep dive? From correct application to how to take care of face skin and everything in between – let’s jump in. 

How exactly does sunscreen work?

The vast majority of sunscreens work because of active UV absorbers. These are chemicals that absorb the UV radiation and transform it into heat before it has a chance to damage your skin. 

Other sunscreen products use UB reflectors, like zinc. Unlike UV absorbers, these types of creams create a barrier on your skin that the UV reflects off. 

If you tend to break out, then select sunscreens that contain more physical blockers.

- Dr Elizabeth Dawes-Higgs, Dermatologist

There are two parts to the UV spectrum – UVB and UVA – so this is why you often see the words ‘broad spectrum’ on sunscreen bottles. This is a good thing!

Of course, these helpful ingredients are mixed with other things, like cream, water, fragrances, preservatives and moisturiser for skin hydration.

For best protection, the Australian Government’s ARPANSA website recommends a combination of sun protection measures including using a broad spectrum, water-resistant SPF30 or higher sunscreen. But what is SPF? It’s simply a rating system that tells you how much protection you’re potentially getting. 

How often should you reapply sunscreen?

A bunch of factors influence the answer to this question, such as what product you’re using, how much sunscreen you apply and what your skin is touching. 

Firstly, experts suggest you apply sunscreen 20 minutes before sun exposure

Also, how you apply sunscreen makes all the difference. A recent study found that, “participants had missed a median of 20% of their available body surface after a single application. After double application, they had missed 9%.” These findings suggest that before intense sun exposure, you should apply your sunscreen twice. 

Dr Liz advises, “Sunscreen runs off easily, so it’s important to reapply.”

What you’re doing during your day may affect the protection you get from your coverage. Getting changed, towelling off, cuddling and swimming can all remove the protective layer. 

It may be preferable to reapply after any vigorous activity that could remove sunscreen, with reapplication potentially every 15-30 minutes. 

But, advice from the Cancer Council is to reapply every 2 hours and immediately after swimming. 

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Experts suggest you apply sunscreen 20 minutes before sun exposure.

Does sunscreen expire?

Just like most things, sunscreens can expire so it might be a good idea to check the use-by date of the sunscreen in your cupboard.

Chuck out and replace any that is past its prime and try to store your sunscreen below 30°C where possible. 

Can you tan with sunscreen on?

The goal of using sunscreen is to protect your skin from the sun. If your sunscreen is working properly then your skin should be protected from all signs of sun damage – including tanning. 

Sun damage contributes to many of the characteristics of ageing skin, so one of the best ways to look good in the skin domain is to avoid the damage. 

If you still want that sun-kissed glow, you could always opt for a fake tanning product, but don’t forget to still use sunscreen!

And if you’re curious how soon you could apply sunscreen after a spray tan? Just chat to your beautician. They should be able to advise which product and application will work well with their formula. 

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Many people aren’t putting enough sunscreen on their skin – you should aim for a teaspoon for each body section.

How much sunscreen should you apply to your face? 

Dr Liz suggests that 5 mL, or one teaspoon, of sunscreen is the right amount for your face and cautions that people generally underapply. 

“Sunscreen testing in the lab involves using a sunscreen dose of 2mg/cm2 area of skin. However, it’s believed that only about 20-50% of this amount of sunscreen is actually applied in practice,” Dr Liz says. 

The Cancer Council recommends about one teaspoon for each:

  • arm 
  • leg 
  • body front
  • body back 

That’s about 35 mL in total. If you imagine a shot glass, it would be overflowing so it’s quite a bit. 

“Remember that it might be easy to miss areas of skin as most products are not visible,” says Dr Liz.

What about oily skin?

If you suffer from oil-related skin issues, you may be wondering what’s the best way to apply and reapply sunscreen to oily skin? Especially if you have mild adult acne.

Dr Liz suggests that what product you’re using is more important than how you apply it. It’s important to choose a product that’s labelled ‘oil free’ or ‘non comedogenic’ – these may have less chance of causing problems.

“If you tend to break out, then select sunscreens that contain more physical blockers, have a lighter base – such as a lotion – and avoid any fragrances. It’s also important to remember to remove the sunscreen at the end of the day,” she says. 

And as always, if you tend to react to new products, talk to a dermatologist about the best skincare for sensitive skin. 

If you have other concerns about your or your child’s skin, read all about face serum benefits and how to have clear skin as a teenager. And if you're not sure where to start, read what is my skin type

How do I apply sunscreen over makeup? 

Did you know that it’s possible to reapply sunscreen over makeup? 

Or, more importantly, that you can practice sun safety and enjoy a full beat? According to makeup professionals, the trick is to apply a good layer of sunscreen under your base. Then, use a sponge to apply a light sunscreen over the top when it’s time to reapply. 

While we are talking about looking your best, you may be wondering – do collagen powders work? Or what the best foods for skin repair are. Or you may be curious about how to turn damaged hair into happy healthy hair? 

Slip, slop, slap and seek + slide. 

Australia has one of the highest UV ratings in the world. For over 10 months of the year in Australia the UV is above 3 – that’s high enough to damage your skin. A good way to remember to use sunscreen is to store your sunscreen next to your toothpaste so you can apply it each morning after you brush your teeth

Just remember – sunscreen is only part of the solution. 

Children of the 90s may remember the Slip, Slop, Slap campaign – slip on a shirt (or other covering), slop on some sunscreen, slap on a hat. Now the SunSmart campaign, jointly funded by Cancer Council Victoria and the Victorian Government, includes ‘seek’ some shade and ‘slide’ on some sunnies. 

Dr Elizabeth Dawes-Higgs is an award-winning dermatologist with extensive experience in the world of medicine, business leadership and education. She is passionate about a range of topics including laser dermatology, the treatment of scarring and skin cancer management.

Reviewed by the healthylife Advisory Board December 2021.

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This article is for informational purposes only and does not provide medical advice, diagnosis, or treatment. Any information published on this website or by this brand is not intended as a substitute for medical advice. If you have any concerns or questions about your health you should consult with a health professional.