My dermatologist is board-certified in three areas of skin cancer and has his patients, many of whom live in Florida, use only the old-fashioned "barrier" sunscreens (zinc oxide and titanium dioxide) as he thinks the newer "chemical" ones (oxy- and avobenzone among others) are inefficient, degrade very quickly in sunlight and there's growing evidence that they are hormone-interrupters. They also get absorbed by the skin whereas the barrier sunscreens do not. And they have a short shelf life after the container is opened, estimated to be less than 18 months by some researchers. But shorter in hot, sunny climates. And they are being outlawed in some areas as reefs are dying off where swimmers are using them.

Dr. C. and his young family all use the Tizo sunscreens as it has an ability to protect against UV-C rays as well.

There was a famous lawsuit against a company making chemical sunscreens. A family vacationing in Florida bought their product, used it scrupulously according to directions and ended up in the hospital with bad sunburns. This suit led the FDA to re-look at sunscreens and the instability of the chemical ones and, as a result, they now require expiration dates on the packaging. So caveat emptor. The sun exposure today is harsher than what our parents grew up with. And if you do nonetheless get a bad sunburn, emu oil works quickly to help limit the damage.