Dr. Eichenfield, who is the past president of the Society for Pediatric Dermatology, called it “having a broad perspective on sun protection.”

When it comes to sunblock, the safest, from the point of view of absorption, are “physical sunscreens,” based on titanium dioxide or zinc, which do not get absorbed like chemical sunscreens.

“The scientific studies still support use of sunscreen to protect against skin cancer, and people who want to be informed should be aware that titanium dioxide and zinc have been judged to be safe,” Dr. Eichenfield said. “They’re not found in the bloodstream, they stay on the skin, they block the sun, there’s no evidence of them being absorbed systemically.”

They are also much more visible on the skin, and many children — and adults — prefer the less visible chemical products. And if the physical blockers are broken down into nanoparticles, to make them more cosmetically acceptable, the concern is that then they also may be absorbed.

There are also some chemicals in sunscreen that have provoked concerns about environmental effects; a law in Hawaii which will take effect in January 2021 bans two chemicals, oxybenzone and octinoxate, which can harm coral.

So the message is to choose your sunblock and then use it, after taking advantage of the other sun protection strategies. “Any skin that gets exposed and can’t be protected by hats and shade and clothing should be protected liberally with sunscreen,” Dr. Weinstein said.

[Read Wirecutter’s reviews of sunscreens for 2019.]

Speaking as a parent and a pediatrician, I would like to acknowledge that this advice is often easier to give than to follow. And it may be that we are not giving it as effectively as we could be, which may also be related to how parents perceive the risk to their own families.