The benefits of sunscreen
Sunscreen is one of the most effective ways of reducing exposure to ultraviolet (UV) radiation, the main cause of skin cancer.
Suncsreen has been proven to reduce the risks of melanoma, squamous cell carcinoma, and solar keratoses. It has also been shown to reduce visible signs of skin ageing.
(Green 2011, van der Pols 2006, Thompson 1993, Hughes 2013)
How does sunscreen work?
Sun damage and skin cancer are caused by ultraviolet radiation in sunlight damaging DNA in the genes of skin cells. Sunscreens help prevent UV from reaching the genes, either by absorbing or reflecting UV radiation.
Physical / mineral sunscreens
Physical sunscreens create a barrier on top of the skin which UV radiation cannot easily penetrate — it reflects off the skin. The active ingredients are usually zinc or titanium (Hanrahan 2012).
Chemical sunscreens absorb UV radiation, converting it into heat which is released from the skin. There are many different formulations, often used in combination because each chemical protects against a narrow range of wavelengths.
Liposomal sunscreens are a relatively new formulation. Small particles contain the UV-blocking component of sunscreen. They absorb into the uppermost layer of the skin, rather than sitting on top of it (but they do not penetrate the skin or enter the bloodstream).
How to choose a sunscreen
Any sunscreen you use should have a sun protection factor (SPF) of at least 30, and provide broad spectrum protection.
Sun protection factor
Sun protection factor (SPF) is a measure of how much longer it takes skin to burn with sunscreen than without. A higher SPF number means stronger protection.
Properly applied, SPF 30 filters 96.7% of UV-B radiation, and SPF 50 filters 98%. The difference is relatively small and need not influence your sunscreen choice if there are other factors which are more important to you.
Broad spectrum sunscreens
UV radiation occurs in different wavelengths – UV-A and UV-B. A good sunscreen blocks a high proportion of both types. SPF only measures protection against UV-B which causes burning. UV-A causes longer-term changes such as wrinkling, drying and ageing of the skin. Both types of radiation contribute to skin cancer development.
Broad spectrum sunscreens protect against both wavelengths of UV radiation. In Australia, most commercially sunscreens with SPF30 or more provide broad spectrum protection, but you should always check that the label specifies “broad spectrum”.
If your sunscreen is broad spectrum and SPF 30 or more, other factors are a matter of personal preference. You should choose the sunscreen that you are most likely to use.
Things that might influence your choice:
If your skin is very sensitive, choose a sunscreen that is less likely to cause irritation. In general, physical sunscreens, “low irritation” sunscreens and sunscreens marketed for children or babies are less irritant
If your skin is dry, you may prefer a cream which combines sunscreen with moisturiser. Alternatively, you can use a very light or “sheer” sunscreen and then cover it with make-up or moisturiser.
Which sunscreen is best for the face?
The skin on the face tends to be more sensitive, so choose a sunscreen that has been formulated for sensitive skin or specifically for the face. Also look for sunscreens that have eliminated unnecessary ingredients like perfume. Ultimately, the only way of being sure how your skin reacts to a sunscreen is to try it and see if it suits. So read the reviews and then do some trialing until you find the right sunscreen.
Which sunscreen is best for a baby?
Baby skin is particularly sensitive, so look for a baby or child specific formulation. Again stay away from perfumed products and test the product on a small section of skin.
Babies have a large surface area in relation to a small volume. If a sunscreen contained irritant ingredients, a large amount could theoretically be absorbed. For this reason, may experts recommend mimimising the use of sunscreen in small babies. However, there's no definite evidence that sunscreens are harmful for babies.
Swimming and sweating
If you are swimming or sweating while outside, a chemical sunscreen will usually last better. Some brands specifically formulate sunscreens for “wet skin” or “water sports”.
If you spend a long time in the sun, particularly if you sometimes forget to reapply, a longer-lasting formulation may be suitable. These include liposomal products, and others containing proprietary combinations of chemical sunscreen components formulated to break down more slowly, e.g. Helioplex in Neutrogena sunscreens.
Aerosol sprays are easy to apply and can be useful for hairy skin or children who might not tolerate having cream or lotion rubbed in to their skin.
These sprays should be applied outdoors where there is less chance of inhalation (Chipps 2016).
Many affordable sunscreens are available in supermarkets and discount pharmacies. Some come in large containers suitable for family or workplace use.
If a sunscreen is labelled as SPF 30 or more, and broad spectrum, it should provide good protection providing it is properly applied.
Some people apply sunscreen and still get sunburnt. Sunscreens on the Australian market are tested to ensure they work as advertised.
The most common cause of sunscreen “failure” is not applying it properly.
Applying and reapplying
Most people don’t use enough sunscreen (Diffey 1996), and they don't cover enough of their body.
For adequate protection, the average adult should use about 45ml or 9 teaspoons of sunscreen:
- one teaspoon of sunscreen applied to the face/head/neck
- two teaspoons for the torso
- one teaspoon to each arm/forearm
- two teaspoons to each leg
Sunscreen should be applied 20 minutes before going outside and reapplied every two hours (Cancer Council Australia 2020).
Pump packs are a good way of ensuring adequate sunscreen is applied. Children using pump packs tend to apply more sunscreen than those using sprays or squeeze bottles (Diaz 2012).
On a cloudy or cool day, it can be easy to forget to apply and reapply sunscreen. We recommend the SunSmart app for smartphones. It can notify the user when the UV index reaches a level which can damage skin, and remind when to reapply sunscreen (Sunsmart Victoria 2021).
It’s common for people not to use enough sunscreen when using a spray-on formulation. Different brands deliver a different amount of sunscreen per second (Cancer Council Australia 2020). To get adequate protection, ensure that you spray enough to feel wet, and then smear it in with your hand.
Sunscreens should be stored below 30° and not used past their expiry date. Do not keep sunscreens in your car.
Sunscreen and vitamin D deficiency
Vitamin D deficiency is common in Australia. Since sun exposure is necessary to produce vitamin D, some people are concerned that using sunscreen may lead to low vitamin D levels. Studies have shown that this is not the case. There is no confirmed link between low vitamin D levels and sunscreen use (Hanrahan 2012).
Potentially any sunscreen could cause problems; it’s not possible to conclusively prove that any product is 100 per cent safe. However, there is strong evidence that the health benefits of sunscreens far outweigh any health risks.
Some ingredients in sunscreens irritate sensitive skin. It can be a process of trial and error to find a sunscreen that causes the least irritation.
- Fragrances can cause irritation. Use unscented sunscreens where possible.
- Physical sunscreens are less likely to irritate the skin than chemical sunscreens.
Nanoparticles are very tiny (less than 100nm) particles of zinc or titanium used in some physical sunscreens. They reduce the white greasy appearance common with physical sunscreens and can be easier to apply. Nanoparticles have not been shown to penetrate the skin.
There is no current evidence that nanoparticles are absorbed into the bloodstream or cause any health problems.
(Hanrahan 2012, Therapeutic Goods Administration 2020).
Hormone disruption and cancer
Some people have raised concerns that the organic compounds (e.g. oxybenzone) used in chemical sunscreens could cause cancer or disrupt the action of hormones. To date, these effects have been seen only in animals during testing at extremely high doses. It would probably be impossible to replicate these doses in humans using sunscreen, even over many years (Chipps 2016).