Australia has one of the highest skin cancer rates in the world. While not everyone chooses to follow the old advice to 'slip, slop, slap', slopping on sunscreen at least has been shown to help prevent skin cancer. But when sunscreen isn't used properly – which usually means not using enough of it, or not reapplying often enough – people may not be getting the protection they expect.

Meanwhile, some people are concerned that sunscreen may actually cause health problems, thanks to the presence of endocrine-disrupting chemicals or nanoparticles.

We take you through some of the myths and facts about sunscreen, as well as what to look for when choosing one, with info on:

UV danger

When you're out in the sun, you're exposed to two forms of UV radiation: UVA and UVB.

UVA penetrates deeply into the skin and is responsible for tanning – it's what's used in tanning bed lights. It also causes skin ageing, wrinkles and some skin cancers. UVA is present at fairly consistent levels during daylight hours all year round.

UVB radiation causes skin reddening and sunburn and is the major cause of skin cancer. It also contributes to tanning and skin ageing. Unlike UVA, UVB levels vary according to altitude, latitude, time of day and time of year.

A broad spectrum sunscreen blocks both UVA and UVB rays. All sunscreens over SPF4 are required to be broad spectrum.

What's in sunscreen?

There are two major types of active ingredient in sunscreens – organic chemical filters and inorganic metal oxides. Just to confuse things though, there are new actives which are organic particles, so are 'chemical' rather than 'mineral', but are in the form of particles like the metal oxides.

Chemical filters

These are chemicals that absorb UV radiation and stop it penetrating your skin. There are some that protect against UVA only, some UVB only, and some that protect against both. Within the UVA spectrum, filters are further divided into UVA1 and UVA2 protection, so you may find more than one UVA filter in a product.

Chemical sunscreens that provide protection over the whole UVA spectrum as well as UVB ares bemotrizinol, also called Tinosorb S or Escalol S and Methylene bis-benzotriazolyl tetramethylbutylphenol (also called Tinosorb M or Bisoctrizole). They have no known endocrine effects and rarely cause skin irritation.

Methylene bis-benzotriazolyl tetramethylbutylphenol (bisoctrizole or Tinosorb M) consists of organic particles which absorb UV, like chemical filters, but also reflect and scatter it, like physical blockers (zinc oxide and titanium dioxide).

Skin sensitivity

Chemical sunscreens can cause irritation and in rare cases even allergies, including (ironically) photoallergy, or sensitivity in the presence of sun! Some of the more allergenic ingredients are butyl methoxydibenzoylmethane, oxybenzone and 4-methylbenzylidene camphor (4MBC). If you're trying a new sunscreen and have sensitive skin, do a patch test on your inner arm and leave it for 24 hours to see if there's any reaction.

Endocrine disruptors?

There's also concern that some chemical sunscreens are endocrine disruptors – that is, they have hormonal effects in humans. These include oxybenzone, octyl methoxycinnamate, homosalate and 4-MBC. While this activity has been shown in animals and tissue tests, the doses used in testing are vastly greater than the amount used – let alone absorbed through the skin – for human sun protection.

Chemical sunscreens used in Australia include:

UVA filters
  • Butyl methoxydibenzoylmethane – also called avobenzone and Parsol 1789 (UVA1 and 2).
  • Ecamsule – also called Mexoryl SX (UVA2).
UVB filters
  • Octocrylene
  • Homosalate
  • Octyl salicylate or octisalate
  • Octyl methoxycinnamate
  • 4-methylbenzylidene camphor (4-MBC).
UVA and UVB
  • Bemotrizinol – also called Tinosorb S (UVA1, UVA2 and UVB).
  • Methylene bis-benzotriazolyl tetramethylbutylphenol – also called Tinosorb M or Bisoctrizole (UVA1, UVA2 and UVB)
  • Benzophenones – oxybenzone and dioxybenzone (UVA2 and UVB).

Inorganic metal oxide sunscreens

Minute particles of zinc oxide or titanium dioxide reflect and scatter UV radiation. While both offer broad spectrum protection, zinc oxide offers better UVA protection (UVA1 and 2) than titanium dioxide (UVA2).

Generally considered safer and better than chemical sunscreens, they're particularly recommended for sensitive skins. However, they can give you a ghostly appearance, leading consumers to either avoid them or use less than is needed to be effective.

Nanoparticles

The micronising process, making the metal particles smaller, has solved this problem of 'ghosting' to a large extent, but has given rise to new concerns – such small particles may fall into the nano range, and these so-called nanoparticles carry their own safety concerns. However, research to date has not found that nanoparticles in sunscreen can penetrate below the outer layers of skin, unless the skin is broken. In addition, manufacturers can coat the nanoparticles so they don't react to form potentially hazardous free radicals. Certainly, the benefits of zinc oxide and titanium dioxide outweigh known risks. For more on nanoparticles, see our article Sunscreen and nanoparticles.

What to look for in sunscreen

SPF 50+

Use SPF 50+ sunscreen for maximum benefit.

Price

All sunscreens on the market must be listed with the Therapeutic Goods Administration and tested and rated according to Australian standard AS/NZS 2604:2012. So the cheapest 50+ sunscreen should provide you with the same protection as the most expensive.

One advantage of a cheap one is that you're likely to use it more freely. On the other hand, more expensive ones may feel more pleasant on the skin – if cheaper ones feel yucky, you may not use them as much.

Type of application

  • Lotions and milks. The majority of sunscreens on the market come in the form of milks and lotions. These have the advantage of being cheap, easy to apply and non-drying. However, they may leave your skin feeling sticky or greasy.
  • Creams. Many sunscreens come in both a cream and lotion (or milk) form, where the ingredients are the same but the consistency differs – creams tend to be thicker, and come in a tube, rather than a bottle.
  • Gels. These are alcohol-based, so won't leave your skin feeling sticky or greasy, although may have a drying effect. They may be more comfortable if you have a lot of body hair.
  • Sprays. These are alcohol-based, so they're non-greasy but may dry your skin. They're easy to apply and great for hairy bodies – but make sure you use enough.
  • Roll-ons. They're easy to apply to small areas, but difficult to apply evenly over a larger area. They're also portable and handy to keep in your bag.
  • Sticks. A sunscreen stick is probably only useful for small areas like the face. It's dry and therefore mess-free (although it's sticky when it's on), and compact enough to keep handy in your bag.

Water resistance

If you're going swimming, look for a product that says it's water resistant. And don't be misled by labels that say "4 hours water resistance", for example – it may well stay on your body for this amount of time, but should be reapplied more frequently for maximum benefit: after swimming or exercise, and otherwise at least every two hours.

Products for children and people with sensitive skin

Sunscreens should only be used on small areas of a baby's skin, and only if there is no other protection available such as clothing and shade.

Some sunscreens are marketed specifically for toddlers, infants and children – they may contain more physical blockers and fewer chemical filters, and therefore be more suitable for sensitive skin.

Sunscreen with insect repellent

Insect repellent can affect your sunscreen. Personal insect repellents containing N,N-Diethyl-m-toluamide (DEET) can reduce a sunscreen's effectiveness by about a third.

Combination sunscreen/insect repellent products are SPF-tested after the DEET has been added, so the product in the package does indeed have the SPF that's stated. However, you'll probably need to reapply the sunscreen more regularly than the insect repellent – in which case use just plain sunscreen.

Spray or cream? Natural or synthetic? Wipes or wrist band? See our mosquito repellent buying guide to see which works best.

Getting the most out of your sunscreen

Most sunscreen failure is down to human error – the best sunscreen in the world won't work if you don't use it properly.

Are you using enough sunscreen?

A sunscreen with an SPF rating of 50+ could be much lower when applied if you don't use enough. When sunscreens are tested, they're applied at a rate of 2mg per square centimetre of skin, which equates to about 35mL (or seven teaspoons) for the average adult body. But many people use less, which substantially reduces effectiveness – and it doesn't help that most brands of sunscreen simply state "Apply liberally" on the packaging.

You need to apply:

  • 1 teaspoon for head and neck
  • 2 for the torso
  • 1 for each arm
  • 1 for each leg.

This gives a safety margin to ensure you're properly covered.

Not applying it often enough, not reapplying after swimming or exercising, and inadvertently rubbing it off on clothing, towels and so on can also reduce its effectiveness.

Top tips for using sunscreen

  • Put it on clean, dry skin 15 to 30 minutes before you go out in the sun to allow it time to interact with your skin. Reapply it just before you go out – you'll increase the amount applied and be more likely to get the stated SPF benefit.
  • Cover all parts of the body not protected by clothing (don't forget your ears, the back of your neck, the backs of your hands and the tops of your feet).
  • Apply it evenly, and don't rub it in excessively – most sunscreens will absorb into the outer layer of skin and don't need to be rubbed in vigorously.
  • Reapply at least once every two hours and after swimming or exercise.
  • Think beyond the beach and pool – use sunscreen whenever you go outdoors for a significant amount of time, such as to the park, a lunchtime walk to the shops, playing sports or gardening.
  • Store your sunscreen at a temperature of less than 30°C. If you leave it in the glovebox of your car or in the sun, it may lose its effectiveness. Keep it in the esky with the drinks, in the shade or wrapped in a towel.
  • Don't use sunscreens that have passed their expiry date as they may have lost their effectiveness.

Don't rely on sunscreen alone

Sunscreen is only a secondary and partial defence against UV radiation. First and foremost, you should try to avoid the sun in the middle of day. If you do go out, wear a broad-brimmed hat, a dense-weave shirt and sunglasses. Seeking natural or man-made shade is part of the latest Cancer Council protection battery of slip (on clothing), slop (on sunscreen at least 30+), slap (on hat), seek (some shade) and slide (on some sunglasses).

Our article on sun safety provides more info on sun protection measures.

Some skin cancer experts are concerned that sunscreens lull people into a false sense of security, and they'll stay in the sun longer – a fact borne out in a number of studies – therefore exposing themselves to the potentially more damaging UV radiation. However, that doesn't mean that you shouldn't use sunscreens – only that you should be aware of its limitations, and not rely on it for complete protection.

How do you use sunscreen?

We surveyed over 600 CHOICE members with questions about sunscreen and other sun protection measures – thank you to all those who took part!

What you told us

71% use sunscreen for protection in the sun. 81% use a hat or other head covering, and 80% use sunglasses. Women were more likely to wear sunglasses (85% vs 77% of men) and sunscreen (77% vs 66% of men), while men were the bigger hat wearers (87% vs 72% for women). Most people (66%) also tried to limit their time in the sun.

59% don't want a tan – either sun or fake. Women are more likely to seek a tan than men. (See our guide to self tanning if you're in the 'fake don't bake' camp.)

76% hadn't heard of the 'teaspoon' recommendations for how much sunscreen to apply – that is, a teaspoon for each limb (this recommendation has increased to two teaspoons for each leg), two for the torso and one for the head and neck. Women (36%) were more likely to be aware of these recommendations than men (14%).

Only 25% apply sunscreen 15 minutes or more before going out in the sun, as recommended.

42% reapply sunscreen at least every two hours when they go out in the sun.

Among those who got sunburned despite using sunscreen (30% of those surveyed), the main reason given was that the sunscreen wasn't reapplied often enough (67%).

60% of women and 38% of men check the ingredients. When we asked if there were any ingredients they prefer to have in a sunscreen, the most commonly mentioned were physical blockers zinc oxide and titanium dioxide. For ingredients people prefer to avoid, nanoparticles were most commonly mentioned, followed by zinc oxide or titanium dioxide, with parabens also rating a few mentions.

Sunscreen is one of the best anti-ageing treatments you can use. Want a bit more help? We report on non-surgical anti-ageing treatments.