Benzophenone-3 provides effective protection against both UVA and UVB radiation. The substance has been available since the 1980s.
“There has been a certain amount of discussion about Benzophenone-3, and it is for this reason not common in Swedish sunscreens. This is a shame, since there are few substances that protect as effectively against UVA radiation”, says dermatologist Helena Gonzalez.
It is known that benzophenone-3 can cause contact eczema, but there is limited knowledge about other adverse effects.
Helena Gonzalez carried out a study in which 26 people applied sunscreen containing 4% benzophenone-3 to the complete skin morning and evening for five days. These people supplied a urine specimen every day.
“We designed the study such that it was similar to what is normal when people take a normal holiday in the sun”, says Helena Gonzalez.
The subjects continued to provide urine specimens after they stopped applying the sunscreen. The urine still contained benzophenone-3 five days after stopping using the sunscreen, a result that suggests that the substance is being stored in the body. The average total amount of benzophenone-3 excreted was 3.7%.
“We don’t know how long it is stored, and we don’t known whether it is important, but I suggest that parents of small children should avoid using sunscreens that contain benzophenone-3, to be on the safe side”, says Helena Gonzalez.
Children under the age of two years have not fully developed the enzymes that are believed to break down benzophenone-3. This suggests, in theory, that small children will not be able to get rid of the substance as easily as adults.
The thesis also shows that several common sunscreens break down under the action of sunlight. Several sunscreens that are readily available in the shops were tested, and their photostabilities were measured after 30, 90 and 120 minutes. The protection against UVA radiation deteriorated by more than 20% for three of these sunscreens. This deterioration took place for one sunscreen after only 30 minutes.
“The principal protection against the harmful effects of the sun should be clothes,” says Helena Gonzalez, “and sunscreens should be used solely as a supplement.”
Some of the commercial sunscreens have changed their composition after the test was carried out, and it is not known whether the new formula has better photostability than the old.
Thesis presented for the title Doctor of Medicine at the Sahlgrenska Academy, Department of Clinical Sciences, Department of Dermatology and Venereology
The title of the thesis: Studies of Sunscreens: Percutaneous Absorption of Benzophenone-3 and Photostability
The thesis will be defended on Friday 10 November, 9.00 a.m., Lecture Theatre “Arvid Carlsson”, Academicum, Medicinaregatan 3, Göteborg, Sweden.