As much as you may plan to run for cover when the sun really starts beating down, sometimes this is simply not an option. If you’ll be outside for several hours in a high-UV environment with no shade—because you’re surfing, hiking, or at a sporting event—you should definitely invest in clothing that is rated as UPF 50+, the highest rating. (UPF is like SPF, but for textiles.) The protection doesn’t come from fancy chemical finishes on top of the fabric, but from the density of the threads in the fabric, Henderson says. So don’t be lured into spending more on clothing coated with titanium dioxide or Tinosorb, or laundry products which promise to coat clothing with UV protection. They can [wash away in the laundry] (https://cen.acs.org/content/cen/articles/90/web/2012/07/Clothing-Leaches-Little-Titanium-Dioxide.html) anyway if not effectively incorporated into the fabric.