Australia has one of the highest skin cancer rates globally, with approximately two-thirds of us diagnosed with some form of skin cancer during our lifetime. As summer approaches, protecting our skin from the sun’s harmful rays becomes even more of a focus. But how do we best do that? Can you still tan with sunscreen on? And, how often do we need to reapply sunscreen?
To answer these and other common questions, we spoke with two leading experts from the documentary Conquering Skin Cancer: Adjunct Associate Professor Craig Sinclair, Head of Prevention at Cancer Council Victoria, and Professor Victoria Mar, Director of the Victorian Melanoma Service at The Alfred.
How do sunscreens work?
Sunscreens are formulated with active ingredients that protect the skin by either reflecting or absorbing ultraviolet (UV) radiation. Sinclair explains, “There are two major types of sunscreens: those that have physical blockers, like titanium dioxide, and those that use chemical absorbers.”
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Physical blockers, such as zinc oxide and titanium dioxide, create a mirrored surface on the skin and are often found in sunscreens that leave a white cast on the skin. “The early generation of those sunscreens sometimes made you look ghostly because what you were seeing was the sun effectively reflecting off the skin,” says Sinclair.
On the other hand, chemical absorbers filter and absorb UV radiation, preventing it from penetrating the skin. This allows it to be formulated in a way that looks invisible on the skin, making it more suitable for everyday use.
What’s the difference between UVA and UVB rays?
“UV radiation consists of different wavelengths. UVA rays have longer wavelengths that penetrate deeper into the skin, while UVB rays have shorter wavelengths. We often remember UVA as ‘A for aging’ and UVB as ‘B for burning’,” says Mar.
UVA rays penetrate the skin more deeply and are primarily responsible for premature skin aging and wrinkles. They can also contribute to the development of skin cancer. UVB rays, on the other hand, affect the outer layer of the skin and are the main cause of sunburn. They play a significant role in the development of skin cancer as well.
“Broad-spectrum sunscreens protect against both UVA and UVB rays, but some components are more effective at blocking different wavelengths, and so often sunscreens will contain a mixture of these ingredients.”
What does the SPF number mean?
Sun Protection Factor (SPF) is a critical measure of a sunscreen’s effectiveness. “SPF is measured by applying sunscreen to human subjects and exposing them to UV radiation. If someone gets sunburned in 10 minutes without sunscreen but takes 300 minutes to get sunburn with it on, the product has an SPF of 30,” explains Sinclair. This means SPF 30 sunscreen allows you to stay in the sun 30 times longer without burning. “SPF 30 blocks out around 96-97 per cent of UV, while SPF 50 blocks out 98 per cent.”
When it comes to choosing a sunscreen, Sinclair recommends making sure it’s water-resistant with at least SPF 30.
How often do we need to reapply sunscreen?
One common misconception is that a single application of sunscreen is sufficient for all-day protection. Sinclair warns, “Sunscreen is not a shield of armour. It can wear off due to activities such as swimming, sweating or towel drying.”
Mar adds: “Water-resistant sunscreen will start to lose its SPF level after about 40 minutes of water immersion, so it will need to be reapplied. Other ingredients in the sunscreen can also significantly affect its durability. For example, a gel-based sunscreen will lose effectiveness more readily with sweating or water exposure.”
“Reapplying every two hours ensures continuous protection,” says Sinclair.
Can you still tan with sunscreen on?
A frequently asked question is whether it’s possible to tan while wearing sunscreen. “Yes, it’s possible because the sunscreen is a filter,” says Sinclair. “An SPF 30 sunscreen might allow about 3 per cent of UV radiation to penetrate, while an SPF 50 might allow around 2 per cent, if applied liberally. Even if people are diligent about applying their sunscreen and spend a lot of time outdoors, they may still develop some form of a tan over a longer period.”
Can you get enough vitamin D while wearing sunscreen?
Many people worry that using sunscreen might prevent them from getting enough vitamin D, which is crucial for maintaining healthy bones and supporting the immune system.
Sinclair reassures us that’s not the case. “Studies suggest that because people don’t apply sunscreen properly or consistently, it doesn’t significantly impact vitamin D absorption. Spending just five to 10 minutes outdoors around midday is usually sufficient for vitamin D synthesis.”
This contrasts with laboratory conditions, where “sunscreen would reduce the likelihood of people getting sufficient vitamin D absorption. But in real life, the studies today suggest it doesn’t make much of a difference.”
What are common misconceptions about sunscreen?
According to Mar, one of the biggest misconceptions is thinking, “I’ve got sunscreen on, I’m protected.”
“It’s important to use sunscreen on areas that are difficult to cover up, but protective clothing, including long sleeves, a hat, and sunglasses, should be used whenever possible. This way, you’re less likely to be caught out by not applying sunscreen correctly or forgetting to reapply.”
Another misconception is that we can feel UV rays, so if it’s not hot, we don’t need to apply sunscreen. “UV is not the same as heat,” says Mar. “We can’t feel UV. UV can be very high even on cool, overcast days.”
What other ways can we protect our skin from the sun?
To maximise sun protection, Sinclair recommends getting into the habit of applying sunscreen every morning and then reapplying when you spend extended periods outdoors. One helpful tool he suggests is the Global SunSmart UV app, which provides real-time UV index information and sun protection recommendations.
Mar adds, “Remember to apply sunscreen to areas that are often forgotten or missed, such as the lips, ears and the top of feet. Since sunscreen can be difficult to apply to large surfaces and hair-bearing areas, protective clothing can provide more reliable coverage than sunscreen. Wear rashies at the beach, long sleeves and broad-brimmed hats rather than caps.”
“It’s important to exercise but schedule your events and activities outside of peak UV periods,” says Mar. “Also, make the best use of shade where possible.”
The bottom line
Sunscreen is a vital tool in our sun protection arsenal, but it should be used correctly and in combination with other protective measures to reduce our risk of skin cancer. Remember to choose a sunscreen that is at least SPF 30, reapply it every two hours, and complement it with hats, clothing, and shade. With these practices, we can protect our skin and maintain its health throughout the sunny months.
Watch the Conquering Skin Cancer documentary in cinemas from December 4.
For more information on staying sun smart download the SunSmart Global UV app to check the UV Index, plan your outdoor activities, and protect your skin.
