The Weston A Price Journal winter 2018 explains the marking, SPF, is a marketing tool for toxic mixtures of skin protection   Freckles welting up or skin blistering shows you’ve gotten into the “unhealthy zone”.  Raises risk of skin cancer. 😕. Marking is used in other countries too.

Look at environmental working group site online ewg.org for better choices. See also 3/3&6/20 for more about Weston A Price.