The government currently allows 17 filters in American sunscreens, nine of which are rarely used, because they have undesirable side effects or because cosmetic chemists find them difficult to blend into the kinds of products that people like. The eight that you will find in the products at your local drugstore still leave something to be desired. “The ingredients that we have to work with can cause some challenges in creating a really elegant formula,” Kelly Dobos, a cosmetic chemist who teaches at the University of Toledo, told me. That’s especially true when filters are used in the concentrations necessary for high SPFs, she said. Maximum protection can sometimes mean maximum chalkiness or oiliness, although a skilled formulator will try to counteract these effects with tweaks to the formula or manufacturing process.

A sunscreen that has an unpleasant texture or turns your skin a strange color might be tolerable for a one-off excursion to the beach or an afternoon in the cheap seats at a baseball game, but it wouldn’t exactly encourage thorough and repeated applications of a sunscreen, which is necessary no matter which product you use. For everyday use, which is widely recommended by dermatologists, the obstacles are even harder to clear, from a formulation standpoint: Oily products don’t play nice with makeup, while chalky products look wild on pretty much everyone, especially people with darker skin tones. Adam Friedman, a dermatologist at George Washington University, told me such concerns are a huge obstacle for his patients. “You can have the best filter in the world,” he said. “If the vehicle in which that ingredient resides is visibly unacceptable or physically unacceptable in terms of application, it doesn’t matter.”