The importance of using broad spectrum SPF 30+ sunscreens in tropical and subtropical climates.

Background/purpose: To evaluate the Sun Protection Factors (SPF) of six sunscreens sold in Australia, using an ultraviolet (UV) spectrum which mimics sunlight as closely as possible, and by using volunteers with a range of skin types to reflect the Australian population.

Methods: Open prospective study. Seventy-five volunteers of skin types 1-3 were tested in a dermatology research laboratory in a major metropolitan teaching hospital in Sydney, Australia in the years 2000-2001. Sunscreen SPF's were measured using a solar simulator and procedures which complied with the Australian Standard.

Results: Sun Protection Factors, as measured by a solar simulator more approximating to natural sunlight than commercial simulators, and using individuals of skin type 1-3, were shown to be approximately between 50% and 80% of their labelled value. Sunscreen application method can also affect SPF measurement.

Conclusion: For a number of reasons, Sun Protection Factors are often overestimated. In addition, many individuals use less than half the amount of sunscreen recommended. Those living in tropical or subtropical climates should be encouraged to use only broad spectrum SPF 30+ sunscreens to achieve adequate protection from the sun.