Sunscreens: mixing them would be a bad idea

Used separately, the sun creams are relatively safe and effective. However, when mixed, the chemical reactions are unpredictable. The mixtures can then let through most UV rays from the sun. Some mixtures could even produce toxic by-products. According to a new study, the combination of a sunscreen with organic filter with sunscreen mineral filter (zinc oxide) is the worst of all.

To test the possible toxicity of sunscreen mixtures, the scientists chose to test them on zebra fish. Not only do these animals have a great genetic similarity with the man, but they also biologically represent all marine fish. These fish are often affected by sunscreens used by vacationers on the beaches.

Note that a strong exposure to ultraviolet (UV) rays increases the chances of getting an skin cancer. The authors of the research therefore recommend the use ofsunscreen when necessary.

A considerable drop in the effectiveness of sunscreens

The researchers mixed the main ingredients that stop UV rays in different sunscreens. They then exhibited the mixtures in the sun during two o’clock. Mixtures composed of organic filters have lost 15.8% of their ability to block UV A rays. UVA rays are present in large quantities in sunlight.

Scientists repeated the same experiment, but this time addingzinc oxide to the mixture. Zinc oxide is marketed as a safe alternative and “Chemical free” to sunscreens. Nevertheless, the results are clear: even with the addition of a small amount of this mineral, the mixture loses 80% (or even 92%) of its ability to protect an individual against UVA rays.

Thereby, Richard Blackburn, a materials scientist from theLeeds University, strongly advise against mixing organic sunscreen withzinc oxide. Therefore, the hybrid sunscreens (combining organic and zinc oxide) should be avoided. In addition, other products such as makeup with SPF (Sun Protection Factor) can alter sun protection products.

A malformation due to sunscreen mixtures?

Regarding the toxicity, the researchers made various mixtures. They then exposed them to zebra fish in the embryo for five days, under the effect of the sun. At the end of the experiment, they noticed a higher concentration of toxic by-products in the embryo when the mixture presentedzinc oxide.

Although the subjects did not die from exposure to these products, they still presented malformations.

In view of the results, the authors of the study insisted on the importance research on photostability and phototoxicity sunscreens. Work on the subject should lead to the development of safer and more effective formulas.