Mixing different sunscreens could almost erase some protection from UV rays, a study suggests.
Experts found that combining “chemical” creams with “mineral” creams containing zinc oxide reduced the barrier they form against the sun by up to 91 percent.
Researchers today warned consumers about the potential interaction, saying the chemical can also be found in SPF products such as moisturizers and makeup.
Independent experts today emphasized the importance of SPF creams and products to block the powerful rays of the sun.
Sunscreen is one of the best ways to both enjoy the sun and protect yourself from a nasty burn and long-term skin cancer risk.
Chemical sunscreens contain substances that absorb UV rays before they reach the skin, causing them to disperse in a chemical reaction.
These products, also called organic or synthetic sunscreens, are absorbed by the body.
While a mineral sunscreen, made from ingredients like zinc oxide or titanium dioxide, forms a physical barrier that prevents UV rays from hitting the skin.
Mineral sunscreens have been advertised as a better choice for those with sensitive skin, such as children, who may experience irritation from chemicals.
Researchers have found that mixing different types of sun protection products can drastically reduce some of the protection provided
Academics at the universities of Oregon and Leeds have tested several SPF 15 sunscreen blends made from ingredients approved for use in the US and EU.
Mineral vs chemical sunscreen. What is the difference?
Also known as organic or synthetic sunscreens, these are the most common type of sunscreen.
They work by absorbing UV light and releasing it as heat.
The following chemicals are found in chemical sunscreens: Oxybenzone, Avobenzone, Octisalate, Octocrylene, Homosalate, Octinoxate
Chemical sunscreen is absorbed through the skin and can sometimes cause irritation.
They should be applied 20 minutes before sun exposure and should be applied regularly.
Sample products: Sun Bum, Nivea, Soltan
Also known as physical sunscreens, these work by absorbing the UV radiation and then scattering or deflecting it, in addition to absorbing the UV light and releasing it as heat.
Two substances are used in mineral sunscreens: titanium dioxide, zinc dioxide.
Mineral sunscreens provide instant sun protection, but can be washed off with sweat and water.
They are less irritable to the skin, but usually require higher amounts to get the same protection as chemical sunscreens.
Sample brands: Alba Botanica, Avène, Hawaiian Tropic
They tested the blends for their level of UVA protection, one element of UV radiation, the other being UVB.
While UVB is responsible for most skin cancers, both types of UV can potentially cause cancer.
The researchers were particularly concerned about one blend, whose formula made up the majority of sunscreen blends used in the EU and US.
They found that it had 90 percent less UVA protection when mixed with 6 percent zinc oxide after two hours of exposure.
In comparison, when the formula was exposed to UV for two hours without the zinc oxide, it only had a 16 percent loss in protective ability.
The scientists found that when exposed to light, the zinc oxide breaks down the other UV-absorbing chemicals in the mixture, diminishing its protective properties.
Study co-author Richard Blackburn said people should still use sunscreen, but be careful about combining different products.
“We still recommend that consumers use sunscreen, but suggest they should be careful not to mix sunscreen with zinc oxide, either intentionally with hybrid sunscreens that combine small molecule UV filters with zinc oxide, or incidentally by mixing sunscreen with other products that contain zinc oxide, such as makeup with SPF,” he said.
The study, published in Photochemical & Photobiological Sciences, also found that the combined sunscreens had higher toxicity after exposure to sunlight in tests on zebrafish embryos.
Fish embryos exposed to the sunscreen mixture containing zinc oxide showed greater changes in their normal development, such as underdeveloped fins and shorter bodies than other sunscreens.
However, when exposed to zinc oxide alone, the fish embryos did not show the same response.
This indicated that it was the combination of the zinc and the other chemicals that caused the toxicity, the scientists said.
They admitted their findings are limited because they didn’t use the exact formulas used by sunscreen manufacturers.
And the team said additives, fragrances and preservatives used in high-street products may react differently.
In the journal, they wrote that more research needs to be done on how different creams behave under different conditions and in combination.
British Skin Foundation spokesperson and dermatologist Dr. Emma Wedgeworth welcomed the inquiry.
HOW TO STAY SAFE IN THE SUN
Sunburn increases the risk of skin cancer.
It can happen abroad or in the UK.
To stay safe in the sun, experts recommend that people:
- Seek shade between 11 a.m. and 3 p.m., when the sun’s rays are usually strongest
- Wear at least SPF 30 sunscreen
- Apply sunscreen for 30 minutes and again just before UV exposure
- If necessary, opt for water-resistant sunscreen and reapply after swimming, sweating or using a towel
- Cover up with protective clothing, a wide-brimmed hat and sunglasses
- Take special care with babies and young children. Babies under six months should be kept out of direct sunlight
- Do not use sunbeds or sunlamps
- Checks moles and skin for any changes
Source: NHS Choices
However, she added that Brits should keep in mind that sunscreen has been shown to protect against skin cancer and there was no evidence that it was toxic to humans.
“We are fortunate to have high quality standards and rigorous testing of sunscreen products available in the UK that are used as directed. I am confident it offers very high protection against harmful UV rays,” she said.
“To date, there is still no evidence that sunscreen is toxic to humans and it is difficult to extrapolate studies in zebrafish embryos to a real-life situation of sunscreen use.”
Other scientists echoed Dr. Wedgeworth.
Professor Winston Morgan, a toxicologist at the University of East London, said that while the study was interesting, he was concerned about the public’s reflexive response.
“My concern is that the public will see the headlines of this research warning against mixing sunscreens and thinking that all sunscreens are not safe, which would be wrong and counterproductive,” he said.
Professor Oliver Jones, an expert in chemistry from RMIT University in Melbourne, Australia, also praised the study as “thought-provoking.”
But he insisted not to exert too much influence on findings with the zebrafish embryos.
“While this is a widely used model for testing ecological toxicity, zebrafish embryos are not mini-humans and the results are not directly comparable,” he said.
“I think the risk of UV damage from not using sunscreen at all is greater than even the worst-case scenario in this study. So, in short, don’t panic and keep using sunscreen.”
About 2,300 people in the UK die each year from melanoma skin cancer, which is mainly caused by overexposure to UV rays.
Of the nearly 17,000 new cases of melanoma skin cancer reported in the UK each year, about 86 percent are preventable, according to Cancer Research UK.