Australia has one of the highest rates of skin cancer in the world, but only two in five Australians use sunscreen with a SPF 30+ or higher, according to recent ABS data.

It’s easy to be confused, especially given the amount of contradictory information around. Here’s what the experts say about when to wear sunscreen, and how much to use.

Will sunscreen stop me from getting enough vitamin D?

Prof Anne Cust, chair of the Cancer Council’s National Skin Cancer Committee, says sunscreen has been shown to limit production of vitamin D when tested in lab conditions. However, she adds, population studies have shown that regular use of sunscreen has little effect on vitamin D levels.

Most people maintain adequate vitamin D levels by going outside for a few minutes most days of the week, Cust says. Vitamin D is also present in oily fish, eggs, and fortified margarines and milk.

Australia’s guidelines around sun safety and vitamin D vary depending on your skin tone and the UV levels. They were changed in February 2024 to recognise that those with “very dark” skin – who need to spend more time in the sun to obtain the same levels of vitamin D – do not need routine sun protection unless they are in the sun for extended periods.

While people with very dark skin do get skin cancers, they are not caused by exposure to UV rays, Prof Rachel Neale from Queensland Institute of Medical Research Berghofer says.

Neale, who led the guideline changes, says that along with vitamin D, sunlight exposure also offers “other emerging benefits”.

She does not recommend that people with very fair skin – who are at high risk of skin cancer – go outside to make vitamin D, even when the UV index is less than three. Instead she suggests talking to a GP about vitamin D supplements, and wearing sunscreen and protective clothing at all times.

Neale says the cut-off point of three is “somewhat arbitrary”, as UV damage is affected by the amount of time spent in the sun and a person’s skin type.

For instance, UV damage can occur “well before” an hour for people with fair skin, even when the UV index is 2.5. For people with olive skin, she says, it may still take less than two hours.

People with neither very fair nor very dark skin should spend a few minutes outside in the early morning or late afternoon with as much skin exposed as possible to get vitamin D. At all other times, they should protect their skin.

She acknowledges this skin-type specific advice can be “difficult to implement”, but says “we have a really high prevalence of vitamin D deficiency, particularly in southern states in winter”.

What sunscreen should I use?

Dr Yousuf Mohammed, a senior research fellow at the University of Queensland, says some products, despite being marketed as sunscreens, are not regulated by the Therapeutic Goods Administration.

It means that certain products, such as some moisturisers that contain SPF, are not subject to the same efficacy and safety standards.

“It leaves our market in Australia open to a lot of abuse, so we need to be careful with what’s available,” he says.

Mohammed says it’s important to use sunscreen with a SPF of 30+ or higher. The SPF level is only an indication of how long a person will be protected. If a person gets sunburnt after five minutes in the sun, a sunscreen with SPF 30+ should protect them for about 150 minutes, he says.

Sunscreens are also known to degrade at certain temperatures, and typically expire within three to six months (as indicated on the packaging).

How much sunscreen should I use, and when should I reapply?

The Cancer Council recommends wearing sunscreen every day when the UV levels are three or higher. They recommend applying sunscreen 20 minutes before going outside, and re-applying every two hours, or immediately after swimming, sweating or towel drying.

Cust stresses that sunscreen alone should “never be used as the first line of defence against UV radiation”. People should also stay in the shade and wear a wide-brimmed hat, sunglasses and protective clothing.

The Cancer Council also “strongly urge against” spray sunscreens, as research shows it is difficult to achieve adequate application with these products. They recommend seven teaspoons of sunscreen for full body application.

Neale says teaspoon measurements might be “difficult to conceptualise” and don’t account for differing body sizes. “I think the best thing to do is to put it on so it feels like there is too much on, and then put more on,” she says.

People believe that if they put sunscreen on in the morning it will have no effect by the afternoon, Neale says, but studies have shown that daily sunscreen use reduces the risk of skin cancer.

I’ve gone my whole life without wearing sunscreen, what’s the point?

According to Mohammed, unless a person has a cancer, there is no damage at the DNA level.

“Cancer only needs a random mutation … and you don’t know when that’s going to happen,” he says. “It might not happen after 5,000 hours of exposure, it could happen after five exposures.

“I don’t think people realise the first sign of burning is a sign you’ve gone too far, it’s the body’s natural defence mechanism asking us to get out of the sun.”

As a bonus, some studies have shown that sunscreen use may reverse signs of sun damage, including wrinkling and skin pigment changes.

Do the chemicals in sunscreen outweigh the benefits?

Neale says there is insufficient evidence to support the idea that chemicals in sunscreen are worse than harms of skin cancer. “There are studies that show chemicals in sunscreen are absorbed” and that “they are also absorbed from other personal care products,” she says. However, “thus far we don’t have clear evidence that they do harm”.

Cust says sunscreens regulated by the TGA are safe to use, as the TGA takes a “conservative approach to regulating sunscreen” and requires that products meet stringent safety criteria.

• This article was amended on 15 December 2024. An earlier version incorrectly stated that chemicals in sunscreen are not absorbed.