With summer starting to creep closer, we’re daydreaming of long days on the beach with cones of soft serve in our hands. 

At one lab in New Haven, Connecticut, though, the talk is all about a major problem that stems from long days in the sun. 

The lab belongs to Mark Saltzman, a professor of biomedical engineering at Yale, whose one-year-old daughter made him take a critical look at the sunscreen he put on her skin. 

“It kind of didn’t dawn on us immediately, but when we started putting large quantities of sunscreen on our daughter, it makes you think about how does it work and where do these molecules go? And we were facing the practical problem of how you deal with sun exposure with a toddler who likes to be outside and likes to be in the sun.” 

Dealing with that problem is actually pretty complicated. 

Right now, your local drug store probably carries two kinds of sunscreens: ones that block the sun’s rays and ones that absorb it. 

The “blockers” basically work like a physical barrier. That’s the white zinc oxide paste that used to be popular decades ago... it’s noticeable, not that attractive, and it feels gritty. 

“So these are classically the ones that you see in beach movies that lifeguards had spread on their nose,” Saltzman says. 

The second category is the sunscreen that most of us actually use. Those sunscreens work by absorbing the sun’s energy with various chemicals. 

What concerns Saltzman is that those chemicals don’t just stay on the surface of our skin. They’ve been detected in both blood and breast milk. 

“Many of these chemicals, if they penetrate into the skin, can generate something called free radicals which can lead to DNA damage in cells,” Saltzman says. “Maybe that DNA damage is rapidly repaired and is of no consequence. That’s certainly possible. Or maybe it’s not.” 

As a biomedical engineer, Saltzman works on getting drugs to the cells in our body where they’re supposed to go. He had been working on a project to create particles that could glide through the body, not sticking to anything. 

Somehow, though, he accidentally got the opposite of what he wanted: incredibly sticky particles. He realized this new sticky stuff might come in handy for keeping sunscreen chemicals on our skin and out of our bodies. 

Saltzman went looking for someone who’s an expert on skin and found dermatologist Michael Girardi. The pair used their new, sticky material and mixed it with regular sunscreen – the kind most of us use all the time. 

They created something that lasted almost five days, which WAY outlasts the sunscreens we use now. And it had far fewer chemicals. 

But it’ll be a while before we see their sunscreen on the beach. 

Saltzman and Girardi are hoping that if they can do this in an expedited way, their sunscreen will be on shelves in just a few years.

Until then - if you want to know what they personally are using to protect themselves from the sun - it's zinc oxide all the way.

"[It does] work," says Saltzman, "but they have these other disadvantages."