The typical way in which most of us apply sunscreen leaves our skin less than half of the expected protection from harmful ultraviolet rays, scientists said.
Recent research has shown that in a typical sunscreen application, only 40 sunscreens are available% of the protection they might expect due to the sun protection factor (SPF). Most skin cancers are caused by DNA damage from UV radiation in sunlight.
The study found that protecting the skin from the harmful UV-induced DNA damage that underlies cancers was only significant when sunscreens were applied at a thickness between 1.3 and 2.0 milligrams per Square centimeter, while most people only apply a coat of 0.75.
Scientists suggest that we could increase our protection by wearing a higher SPF to compensate for the tendency to apply sunscreen too thin. "Given that most people do not use sunscreen as tested by manufacturers, it's better for people to use a much higher sun protection factor than they think necessary," said study leader Antony Young, a professor of experimental photobiology at King & # 39; ; s College London.
Quoted SPF ratings are based on the assumption that sunscreen in a thickness of 2 milligrams per square centimeter will be used according to the manufacturer's recommendations, but the average sunscreen user typically uses much less according to previous studies.
"People are typically much less protective than they think," said Young. "For example, if you were to receive SPF20 and use it at a lower thickness of 0.75 milligrams per square centimeter, your protection level could be as low as that of SPF4."
To Investigate What Protective Sunscreen Looks Like When It Is Applied The closer people's everyday lives are, the higher the DNA damage in the skin of 16 subjects who wore different sunscreen layers on UV exposure.
The study participants were divided into two groups of eight: one group received only a single dose of UV radiation to mimic the sun, and the second group received multiple doses over five days to mimic a continuous vacation exposure.
Volunteers received their UV radiation doses within 15 minutes Their sunscreen was applied and skin biopsies were taken immediately after UV irradiation. The sunscreen tested in the study, published in the journal Acta Dermato-Venereologica, complied with EU regulations.
The scientists also varied the UV radiation during the experiment to replicate the conditions in classic holiday destinations such as Tenerife. Skin biopsies showed that those in the "holiday group" who wore sunscreen in the higher thickness recommended by the manufacturer had the greatest protection against damage even after exposure to UV rays for several days
"There is no doubt that sunscreens provides important protection against the carcinogenic effects of the Sun's ultraviolet radiation, "said Young. "Research shows, however, that the way sunscreen is applied plays an important role in its effectiveness."
Nina Goad of the British Association of Dermatologists said: "This research shows why it is so important to select a SPF of 30 or more. Theoretically, a SPF of 15 should be sufficient, but we know that we are in real situations Need the extra protection that a higher sun protection factor provides.
"An additional consideration is that we apply sunscreen prone to missing skin areas, as well as being applied too thinly.
She added that people should not only rely on sunscreen as a sunscreen, but also on clothing and shade.