Health & beauty
Sunscreens
Introduction
Sunscreen alone won't protect you from skin cancer. We explain why - and answer common questions about sunscreens.
Despite years of sunscreen promotion and use, skin cancer rates haven't fallen. It's not the fault of the sunscreens - it's the way we use them that's the problem.
We take a closer look at the issue, plus we explain what to look for in a sunscreen and how much to apply.
June 2008 update: We've tested the SPF claims of 10 sunscreens - and some have failed to meet their claims. Find out more.
What is the problem?
Twenty years ago 814 new cases of malignant melanoma, the most dangerous type of skin cancer, were registered. That's an age-standardised rate of 21.2 per 100,000 of the population. In 2004, the year for which the most recent figures are available, there were 1896 new registrations - a rate of 33.2 per 100,000.
Much of the increase can be explained by the time lag necessary for melanoma to develop. Rates for those 45 years and older have climbed dramatically as baby-boomers pay for summers spent in search of the perfect tan. But in 2004 there were 82 new registrations of melanoma in 30- to 34-year-olds, a rate of 28.0 per 100,000. It was the most common cancer in 15- to 24-year-old women. These are people who grew up after the dangers of ultraviolet (UV) radiation from the sun were well known.
Given the long-running public campaign to warn people of the dangers of sun exposure, what's the problem?
Sunscreen alone is not enough
The Cancer Society of New Zealand's Dr Judith Galtry says we rely too much on sunscreen alone. Protecting yourself when UV radiation levels are at their peak - in the daylight-saving months, especially between 11am and 4pm - involves more than one strategy.
"Sunscreen shouldn't be the only (or even the first) line of defence," she says. "It's very important but it's complementary to limiting your time in the sun and using hats and cover-up clothing."
Studies have shown a reduction of two types of skin cancer in "careful and regular" sunscreen users. But many people aren't using their sunscreen to reduce their UV exposure. Instead, they use sunscreen to stay out longer in the sun without burning. Some UV rays always get through, adding to the damage your skin has already suffered.
Irresponsible claims?
We think these label claims are irresponsible because they encourage people to think they can stay out in the sun for long periods.
"SPF 70"
The Australia/New Zealand Standard allows SPF claims of no more than 30+, and the proposed US Federal Drug Administration regulations limit claims to SPF 50+ as it says this is the highest that can currently be determined by accurate and reproducible testing. Increases in SPF values above 50 provide little extra protection.
"Sunblock"
The European Commission and the proposed FDA rule ban the use of terms such as "sun block" to imply a sunscreen gives total protection. Even high SPF products let some UV radiation through.
"Daylong" and "10-hour protection"
This goes against the advice of Australasian, European and US authorities to reapply sunscreen regularly - every two hours. The European Commission says there should be no claims such as "all day prevention". Sunscreen protection diminishes over time and people simply don't apply enough.
Daylong is sold as a "Kids' Formula". In our view this is doubly irresponsible.
What to look for on the label
You need to choose a good sunscreen for back-up protection. Here are some tips for what to look for.
- "SPF" - which should be 30+ to 50+.
- "Broad spectrum" or "UVA protection".
- A standard that the product's been tested against (although Australian-made sunscreens might not declare this - see "Why do I need to look for a standard?").
- "Water resistance" for when you go swimming or sailing.
- Check expiry dates - don't buy a product without one. Once opened sunscreen should be thrown out after 12 months.
Getting the coverage right
That adds up to about 35 ml for a full-body application (pictured far right).
Frequently asked questions
What difference does the SPF make?
"SPF" stands for "sun protection factor". It's a measure of protection against mainly UVB rays, the ones that cause sunburn. The higher the SPF number, the greater the protection - up to 50+.
Above SPF 50+ the additional protection is very small. In fact, high SPF values are a problem. Studies have shown that people use them to stay out longer in the sun, using sunburn as a warning to take cover. During this time you can receive large doses of UVA radiation.
The current Australian/New Zealand standard limits SPF claims to 30+. Other international standards limit them to 50+.
What does "broad spectrum" mean?
Broad spectrum sunscreens protect against UVA and UVB radiation. Both contribute to premature skin ageing, damage to the immune system and skin cancer.
UVA radiation penetrates deep into the skin layer; it's dangerous because there's no immediate warning sign (such as the sunburn caused by UVB rays).
Why do I need to look for a standard?
Testing the sunscreen by an accepted method shows whether it'll provide the protection it claims. Australia, the US, Britain and the EU have regulations that set standards for the formulation, testing, performance and labelling of sunscreens.
Sunscreens manufactured in Australia might not carry a standards label as all Australian sunscreens must comply with the joint Australian/New Zealand Standard AS/NZS 2604:1998.
US manufacturers will have to comply with the proposed Federal Drug Administration regulations once these are published.
New Zealand has no requirements for sunscreens. Manufacturers here don't have to back up their claims with test evidence or meet labelling requirements.
We've said before that sunscreens should be classified as a therapeutic product and that there should be mandatory compliance with a recognised standard. The Ministry of Health is now considering a revised Therapeutic Products and Medicines Bill. We strongly recommend it requires sunscreens to comply with a standard
Will the sunscreen protect me all day?
No - sunscreen can be sweated, washed or rubbed off, the chemicals may break down over time, and people simply don't apply enough (see Getting the coverage right). You should reapply sunscreen every two hours.
Does having a tan mean you don't need as much sunscreen?
No. A tan is a sign that skin damage has already started. Any further UV radiation will only add to the damage, resulting in wrinkled leathery skin and possibly skin cancer later in life.
Do I need a special sunscreen for my child?
Proper protection from the sun is more important during childhood than at any other time in life. Childhood and teenage sunburn is a high-risk factor for developing melanoma.
Sunscreens that are specially formulated for children have a mild base designed especially for their sensitive skin. But there's no reason why children shouldn't use the family sunscreen, provided it doesn't irritate their skin. Test a small amount on the inside of their forearm first.
Keep babies and toddlers out of the sun as much as possible. The best protection for them is staying in the shade and using cover-up clothing - as it is for everybody.
Sunscreen nanotechnology
Powders of titanium dioxide or zinc oxide form a physical barrier against the sun's rays. They reflect UVA as well as UVB rays and reduce the need to use chemicals that may irritate the skin.
In the past they came as thick white pastes that were messy to use and left a ghostly white sheen on your skin. Then scientists found that shrinking the particles of these two ingredients to less than 100 nanometres (a nanometre equals one millionth of a millimetre) made them transparent while keeping their sunscreen action.
But nanoparticles are tiny enough to slip through cell membranes of the skin.
Concerns have been raised that if nanoparticles of zinc oxide or titanium dioxide are absorbed into skin cells they could possibly interact with sunlight to increase the risk of damage to these cells. The Australian Therapeutic Goods Administration has said this would be a concern only if the nanoparticles penetrated living skin cells. "The weight of current evidence is that they remain on the surface of the skin ..."
However, it's not known whether skin damaged by eczema, acne or cuts is more vulnerable to penetration.
Unfortunately, most sunscreens don't say whether or not any titanium dioxide or zinc oxide they contain is in nano form. So if you want to avoid exposure to nanoingredients, choose sunscreens that don't list them on the label.
If a sunscreen containing either of these ingredients is transparent when applied, it probably contains nanoparticles. The word "micronised" on the label is also a clue.
More information
- Cancer Society of New Zealand: www.cancernz.org.nz
- Information on skin cancer: www.sunsmart.org.nz
- International Council on Nanotechnology: http://icon.rice.edu
Report by Bev Frederikson.