Original Article here: Sunscreen Use and Sweat Production in Men and Women
Take Home Message: Athletes need to use sunscreen when exercising outdoors; however, they need to be selective and ensure the sunscreen is not impeding effective sweating. Sunscreen with titanium dioxide impedes sweat production and may effect thermoregulation.
Sunscreen is imperative for athletes to be protected from solar radiation during physical activity, particularly in hot environments. Several researchers investigated clothing to protect from solar radiation without compromising sweat production and evaporation, but there is minimal research examining the effects of sunscreen. Though the use of sunscreen is advocated, there has been no research on sunscreen’s influence on sweat production and evaporation. Therefore, the authors measured the effects of 2 water-resistant sunscreen products on local sweat production among 20 athletes (10 males, 10 females) following 20 minutes of cycling (78-80% maximum heart rate) in the heat (30o C; 58% relative humidity). They compared these effects with the application of an antiperspirant, which inhibits sweat production. The athletes reported to the laboratory on 2 consecutive days at the same time, and their urine specific gravity and dry body mass were recorded. The researchers used both subscapular regions, which allowed 2 treatments to be randomly tested during each session: sunscreen A (active ingredient,), sunscreen B (active ingredient, titanium dioxide), no lotion, and antiperspirant. As the sunscreen was drying (~60 minutes) the authors measured the athletes’ temperature and applied sweat patches over the applied lotion. After the exercise the authors removed the sweat patches, weighed the athletes, and recorded sweat-collection time to calculate local sweat rate. The authors found scapular localized sweat rate was lower for the antiperspirant and sunscreen B compared with sunscreen A or no lotion treatments.
The authors revealed that certain sunscreen can alter sweating and evaporation that is necessary for thermoregulation. Application of sunscreen B, with titanium dioxide, to the skin hindered sweat production to the same extent as an antiperspirant. Sunscreen A, with oxybenzone, had no measurable effect on local sweat rate when compared with the use of no lotion. Both sunscreens were commercially available with the same SPF; however, they differed in active ingredients. The antiperspirant decreased local sweat rate 25.5%, where sunscreen B reduced local sweat rate by 17% and sunscreen A reduced it by only 12.5%. Though, it is difficult to determine if this difference is clinically significant, or which active ingredients within the sunscreens are primarily impacting thermoregulation, deciding which sunscreen to use is an important factor to consider when preparing athletes for outdoor activities. These changes in local sweat rate could lead to increased risk for heat illnesses. Therefore, medical professionals should consider advising athletes who are active outside in the heat to limit the use of antiperspirants and sunscreens with the active ingredient titanium dioxide on large skin areas. Additionally, medical professions should continue to educate athletes on proper hydration, acclimation, and implementing sunscreen use during outside physical activity.
Questions for Discussion: Do you provide sunscreen or sunscreen education to your athletes? Have you considered that sunscreen could hinder thermoregulation? If so, have you seen a sunscreen that is best for outdoor physical activity?
Written by: Jane McDevitt, PhD
Reviewed by: Jeff Driban
photo credit: http://www.consumerreports.org/cro/magazine-archive/2010/july/health/sunscreens/overview/index.htm