This Fourth of July, millions of Americans will conscientiously slather on sunscreens before heading out for fun in the sun at beaches and picnics.

For decades, we’ve been advised that sunscreens are our best defense against the painful sunburns that can lead to skin cancer.

But world experts are increasingly saying sunscreens alone can’t protect us and we have to starting using additional methods to safeguard our skin. And although avoiding sunburn is good, it doesn’t mean we won’t get sun-induced skin cancer.

“Sunscreens do prevent sunburns, and sunburns cause skin cancer, but people can still get skin cancer from UV exposure in the absence of sunburn,” says DeAnn Lazovich, a School of Public Health associate professor and an expert on tanning, sun protection, and skin cancer.

If people think using sunscreen is the only thing they need to do to prevent skin cancer, they are actually going out into the sun with a false sense of security. Even with sunscreen on, people could be exposing themselves to dangerous levels of UV, and consequently, increasing their risks of developing skin cancer.

Across America, five million people are diagnosed with some form skin cancer each year, and of those, 9,000 people die from its deadliest variant, melanoma.

Lazovich has extensively researched melanoma risk and sunscreen use among Americans. She’s a national authority on the subject and her research has informed the skin cancer and sun safety recommendations of state and national agencies—all the way up to the Surgeon General’s office.

Lazovich says that to reduce skin cancer risk, Americans’ must take other precautions against the sun first and use sunscreen as a last resort.

She advises following World Health Organization (WHO) guidelines to avoid sun exposure:

• Wear tightly woven clothing that covers the arms, torso, and legs
• Don a hat that shades the entire head
• Seek shade whenever possible
• Avoid outdoor activities during periods of peak sunlight
• Lastly, use sunscreen in conjunction with the above measures

When choosing to use sunscreen, Lazovich recommends looking for products with right mix of protection and ingredients, and to apply them properly:

SPF 30-50: Choose sunscreens with a sun protection factor—SPF—of 30-50.

“Anything beyond 50 isn’t necessary and it’s just more expensive,” says Lazovich.

Select broad-spectrum UVA/UVB sunscreens: The FDA mandates that all current sunscreens protect against both UVA and UVB rays from the sun. Still, check the sunscreen’s label to see if it qualifies as broad-spectrum.

Choose mineral-based sunscreens over chemical versions: Use mineral sunscreens with an active ingredient of zinc oxide or titanium oxide that act as barriers to sunlight.

Avoid chemical sunscreens that contain active ingredients like oxybenzone or avobenzone that can be absorbed into the skin.

“The problem with some of the chemical sunscreens is they can cause hormone disruption in the body,” says Lazovich.

Use enough sunscreen: As a rule of thumb, apply one tablespoon of sunscreen to each of the large body parts, like legs and back. Use one teaspoon of sunscreen on smaller areas such as the face.

“If you don’t use the right amount, you could be getting only a quarter to half of the SPF protection listed,” says Lazovich.

Reapply sunscreen as directed: Read the label to see if the sunscreen is water-resistant and how often it should be reapplied.

“Reapply it every two hours or more frequently if you’re in the water or sweating heavily,” says Lazovich.

Do not use spray sunscreens: Spray sunscreens seem really convenient and easy to use, especially with small children, but they’re difficult to control and also create a possible inhalation hazard for kids.

“There’s no way of knowing how much sunscreen you’re getting on your child with a spray. With a cream, you have it in your hand and know how much it is, and can see where it’s going on their body,” says Lazovich.

Avoid sunscreens containing Vitamin A or Retinyl: Some sunscreens contain the ingredients Vitamin A or Retinyl that act as a skin conditioner. The ingredients, however, have been shown to actually trigger the formation of skin cancer cells when exposed to sunlight.

For a rating on the effectiveness and toxicity of various brand-named sunscreens, visit the Environmental Working Group.