Whether you’re spending your day at the beach, hiking, or enjoying a backyard barbeque, you likely pack a bottle of sunscreen. 

You know it’s important to avoid sunburns to prevent skin cancer, but how do you know you’re fully protected?

Dr. Rebecca Tuttle, a surgical oncologist, explains the difference between physical and chemical sunscreens and shares what to remember when in the sun. 

Physical vs. chemical sunscreen 

There are two types of sunscreen: physical and chemical. 

Physical sunscreen sits on the skin and acts as a barrier against sun exposure. 

“It just creates a layer between your skin and the sun,” Dr. Tuttle says. “Almost like an umbrella or your shirt.” 

Most physical sunscreens are made with the mineral zinc oxide, which can cause a white cast when applied. Because of this, those with darker complexions may prefer to use a chemical sunscreen. 

Instead of sitting on the skin, chemical sunscreens sink into the skin and absorb UV rays. They then convert the rays into heat and expel them from the body. If the word “chemical” gives you pause, don’t worry. Dr. Tuttle explains that all chemicals used are FDA-approved and safe for everyone. But those with sensitive skin may do better with physical sunscreen. 

As for sun protection factor (SPF) in cosmetics, it’s enough sun protection if you spend most of your day indoors. 

“But if you’re doing anything where you’re going to be outside,” Dr. Tuttle says, “then no, that SPF 15 inside your makeup or lotion is not enough sunscreen.” 

Other considerations 

It’s often thought that higher SPF protects your skin better. However, Dr. Tuttle explains that SPF 30, one of the lowest SPFs available, blocks about 97% of UV rays. 

“You get very incremental increases as you go up,” she explains. 

Instead, focus on consistently applying enough sunscreen. You should use one ounce of sunscreen (about as much as a standard-size medicine cup) to cover your entire body and reapply every two hours, sooner if you are swimming or sweating heavily. 

Remember the often-forgotten spots, such as the scalp, ears, eyelids, and feet. And contrary to popular belief, you still need to apply sunscreen to your lower body when spending all day in the pool.

“Water acts as both a reflector and a magnifier,” Dr. Tuttle says. “It is not protective from the sun.” 

Don’t let an overcast day fool you, either. Even though you might not feel hot, UV rays can pass through clouds and burn you.  

Your doctor can answer any questions you have about skin cancer and sunscreen.