How to pick the right sunscreen — and which ones to avoid

Summertime means picnics, jumping off the dock, boat rides and lots more outdoor fun in the sun.

But those long hours spent soaking up rays can lead to painful sunburn — or worse. Melanoma rates have tripled over the past three decades, according to the National Cancer Institute. And just a few bad sunburns in childhood can double your risk of getting skin cancer later in life.

Using a good sunscreen can help protect skin from exposure to harmful ultraviolet rays. But with about 750 sunscreens on the market, the choices are daunting.

To help us better navigate the sunscreen aisle, we turned to the Environmental Working Group (EWG). The consumer watchdog organization just released its annual sunscreen guide (ewg.org/sunscreen), finding that nearly three-quarters of the products tested this year offered inadequate protection or contained ingredients that may harm the skin.

But with some careful label reading, it's possible to pick an able sun-blocking partner to help you and your family stay safe this summer. Here are the answers to common questions about sunscreen:

Q: How much should I use?

A: More than you think. The SPF values listed on the product labels are measured using a very thick coating of the product, explained Sonya Lunder, a senior analyst with EWG.

"Unless you're putting on a lot, you're not going to get close to the value on the bottle," she said. Recommended amounts vary depending on the size of the person and skin exposure, but in general, an adult wearing a swimsuit needs the equivalent of a shot glass full of sunscreen.

Just as important as how much to use is how often to apply it. Because sunscreen tends to rub or wash off — there's no such thing as a waterproof sunscreen — it's best to reapply every two hours.

Q: What about products that combine bug spray with sunscreen?

A: Not recommended.

The reason, said St. Paul dermatologist Dr. Pierre George, is that sunscreen should be applied every couple of hours. Insect repellents typically contain DEET, a strong chemical that could reach toxic levels if applied to the skin as frequently as sunscreen. He suggests using two separate products, rubbing the sunscreen on first. Then add the bug spray — and it's better to apply it to clothing rather than directly onto the skin. Reapply separately, as needed, being careful not to overdo it with the bug spray.

Q: Which ingredients are effective — and safe?

A: Sunscreens typically fall into two categories: mineral-based and chemical-based.

The ones with minerals are better for kids because they produce lower rates of skin allergies and reactions, Lunder advised. Typically, they contain zinc oxide or titanium dioxide as active ingredients. Products with zinc oxide also hold up better than chemical sunscreens, which tend to break down under the sun.

The downside with mineral sunscreens is they usually leave a white, chalky residue on skin, causing some people to avoid them.

Watch out for two common — and potentially toxic — ingredients: oxybenzone and retinyl palmitate. Oxybenzone is a hormone disrupter that mimics estrogen.

Retinyl palmitate, a form of Vitamin A, is said to bolster the body's defense system against ultraviolet A rays. But, Lunder cautioned, a federal study found that animals exposed to this ingredient and UV light had more skin tumors and lesions than other animals whose skin was not treated with it.

Q: What level of SPF protection do I need?

A: Many sunscreens claim they have SPF values of greater than 50. But the EWG report took issue with those claims, noting that other countries have banned products with SPF values higher than 50.

"No sunscreen can reliably protect you for more than two hours," Lunder said, "so nobody needs an SPF value of higher than 50."

Q: At what age can I start putting sunscreen on my child?

A: Six months. Children younger than that have very tender skin. "Kids overheat quickly at that age," Lunder said. "It's much better to cover them up and keep them out of the sun."

Q: Spray or lotion?

A: Sprays are popular, especially with parents who know how hard it is to get complete coverage on fidgety kids. But Lunder said lotions offer better coverage than sprays, which provide only a light coating of protection. He also warned that with spray cans, it's easy for you or your child to accidentally inhale the chemicals emitted as you apply it.

Q: What else can I do to protect my skin from sun damage?

A: Think of sunscreen as a last resort.

Seeking shade and staying out of the direct sun during peak hours — 10 a.m. to 2 p.m. — offers the best protection. Another foolproof method: Cover up. Wear a hat, sunglasses and lightweight clothing.

"Wearing a light shirt offers better and more stable protection from UV rays than sunscreen," Lunder said. "Our goal is for people to have a more realistic expectation of what kind of protection sunscreen offers — to not rely on it as a first line of defense."