Even dermatologists are best able to compare the effectiveness of sunscreens when presented with SPF values, a recent study suggests.
The doctors tended to underestimate the effectiveness of sunscreens when they were presented with information on how much radiation is absorbed by the sunscreen, say the authors.
“Ultraviolet (UV) radiation exposure from the sun and artificial UV sources is the major cause of skin cancer and premature skin aging,” lead author Stefan Herzog told Reuters Health in an email.
“The sun protection factor (SPF) is the best known sunscreen parameter. It conveys a sunscreen’s effectiveness in protecting against the UV radiation that causes sunburn,” said Herzog, a researcher at the Max-Planck Institute of Human Development in Berlin.
Herzog said the UV radiation that causes sunburn is also known as is erythema (redness)-inducing radiation, or EIR.
“The SPF is defined as the ratio of the EIR dose that induces the first visible redness on sunscreen-protected skin to the EIR dose that induces the same redness on unprotected skin,” Herzog said.
Herzog said that when it comes to skin damage, what matters is how much of the radiation is transmitted through the sunscreen to your skin and not how much is absorbed by the sunscreen.