People going outdoors wearing high protection sunscreen lotions may be better protected than people wearing normal sunscreen lotions. Archives of Dermatology published the research report in the topic .
Sun exposure is the most important environmental factor involved in the development of skin cancer, says the background information in the article. Although daily sunscreen use has been shown to prevent squamous cell skin carcinoma, some believe that higher protection by stronger sunscreens may encourage more time in the sun by delaying warning signs such as sunburn, giving one a false sense of safety.
Researchers from the Hôpital Saint Louis, Paris, had conducted a weeklong, randomized, controlled trial during the summer of 2001 to determine the effect of sunscreen protection on sun-exposure behavior. Three hundred sixty-seven vacationers from four French seaside resorts were given one of three sunscreens: SPF 40 labeled as "high protection," SPF 40 labeled as "basic protection," and SPF 12 labeled as "basic protection." No mention of actual SPF was made on the labels. Participants were given an initial questionnaire about general sun-exposure behavior and completed self-administered questionnaires each evening, detailing their sun exposure and protection for every half-hour period during the day. Eighty percent of the participants were women, with an average age of 39 years.
The researchers found that neither SPF nor labeling was associated with significantly different durations of sunbathing during the week. Average weekly sun-exposure time was 14.2 hours in the high/SPF 40 group, 12.9 hours in the basic/40 group, and 14.6 hours in the basic/12 group. Ninety-six percent (343) of the vacationers said they'd used the sunscreen at least once, with 77 percent (276) saying they used it exclusively. The proportion of those who experienced sunburn during the week was higher in the low-SPF group (24 percent) than the high-SPF group with the same label (14 percent). In total, 63 participants experienced sunburn, with six of them having severe sunburn.
The findings do not support the hypothesis that a higher SPF induces a higher exposure by delaying the alarm signs or the hypothesis that mentioning 'high protection' on the label may induce longer exposure by giving an impression of safety. The study logically confirms that the use of higher-SPF sunscreens does reduce the number of sunburns in real life. The results also suggest that people tend to self-regulate their sun protection with sunscreens, by inversely adapting the amount of sunscreen to the SPF, at least when sunscreens are freely delivered.