When we were kids, a day at the beach always began with the same humiliating ritual. Our mom would pour herself a fistful of sticky sunscreen and vigorously slather it all over our bodies. Not even our faces were spared. When the kids were good and gooey, mom repeated the process on herself. 
We were all smeared from the same massive bottle, some generic brand with an awful odor. We get it. Our mom was just trying to protect us from the hazards of sunlight, which are very real. The National Cancer Institute warns that “exposure to UV radiation causes early aging of the skin and skin damage that can lead to skin cancer.” Of course parents want to protect their children. According to dermatologist Doris “No Relation” Day, who recently spoke to Reader’s Digest, dear old Mom might have been subjecting us to a whole new set of risks when she shared her sunscreen—especially when it came to our baby siblings. 
“Babies need to have physical protection such as protective hats and clothing,” Day said. “They have a lower body surface-to-volume ratio, so anything that’s applied topically has a greater chance of penetrating and impacting them systematically.” That’s why pediatric dermatologist Patricia Treadwell recommends avoiding chemical sunscreens like the ones many adults use.
To clarify, there are two general types of sunscreen on the market these days: chemical and physical.
Chemical sunscreens absorb into your skin like a fine lotion, so they must be applied 20 or 30 minutes before exposure. These substances contain chemicals like avobenzone or oxybenzone, which absorb UV radiation before it can damage the skin. 
Physical sunscreens, on the other hand, simply deflect the sun’s rays with zinc oxide or titanium oxide (or both). More properly known as sunblock, these pastes coat the skin with a thick white layer of schumtz. It’s not beautiful, and some people even find it uncomfortable, leading to the popularity of chemical-based sunscreens.
Many doctors say that you should never use chemical sunscreens on your children.
If you prefer these residue-free lotions, that’s probably fine. Just make sure you only use zinc or titanium sunblock on your kids. 
“The chemically based screens are absorbed into the skin in order to protect the skin from UV rays,” plastic surgeon Norman Rowe told Reader’s Digest. “These chemicals can be harmful in high doses to infants and children.” Considering that the higher the sun protection factor (SPF) rating of chemical sunscreen, the higher the dosage, it makes sense that sunblocks are better for growing children. “Zinc oxide blocks are generally the best, as they are not absorbed by the skin, making it one of the safest sunscreens for kids,” Rowe said.
Day agrees.
Infants shouldn’t be in the sun very much until they’re at least six months old, she said. 
“Once they reach about six months it’s considered safe to use a physical protection sunscreen like those containing zinc or titanium, and always choose SPF 30 or higher,” she said. Come to think of it, our dear old mom was probably using a zinc oxide sunblock on those visits to the beach so long ago. We’re sorry we doubted you, Mom!
