How does sunscreen work?

If you’re going to be out in the sun, sunscreen is a great way to protect your skin. Ultraviolet radiation from the sun damages skin cells. This can led to sunburn, aging and even skin cancer.     

Types of sunscreen

Sunscreens combine different ingredients to help stop UV rays from damaging your skin. There are two categories of sunscreen ingredients, says Saira George, M.D., a dermatologist at MD Anderson Cancer Center.

• Physical blockers: The physical blockers – titanium dioxide or zinc oxide – are minerals that are ground into fine particles.  They sit on the surface of the skin and reflect UV rays away from your skin, “a lot like a shield or mirror would,” George says.
• Chemical  absorbers:  Chemical (or organic, meaning carbon containing) sunscreen ingredients form a thin protective film that absorbs UV radiation before it penetrates the skin.  

Is one type of sunscreen better than the other?

There are benefits to both types of sunscreens. In fact, many sunscreens that you find at the store are a combination of the two types.

Physical sunscreens generally do not cause irritation, stinging or allergic reactions. But they can be white and greasy. The chemical sunscreen ingredients are usually clear and easy to apply. But these are more likely to cause irritation and allergic reactions.

So, many sunscreens contain a combination of the two to maximize the benefits of but minimize the downsides. And many broad-spectrum coverage sunscreens need a combination of ingredients to protect against both UVA and UVB rays, the two types of rays that cause skin damage.  

Is sunscreen safe?

When it comes to sunscreen, the benefits outweigh any potential risk. Studies show that sunscreen can help prevent skin damage, which can lead to skin cancer. One in three cancers diagnosed worldwide is skin cancer, according to the American Cancer Society. And up to 95% of malignant melanomas are caused by excessive sun damage, according to a study by the International Agency for Research on Cancer.

Regardless, George says many patients still ask about the necessity or safety of sunscreen.   

“I understand the concern.  What’s more natural than sunlight? But we have to understand that there are carcinogens in nature, and too much UV radiation from the sun is an example of that,” she says. “Our bodies have amazing protective mechanisms in place to handle sun damage, but they haven’t evolved to overcome damage from the excessive sun exposure many of us rack up in our lifetime.”

Studies show that the chemical and nonchemical sunscreens available today all appear to be safe.

“We have lots of evidence to support sunscreen’s protective effects and very little that show any dangers or risks from sunscreens use, but I can sympathize with concerns about chemicals in everyday products,” George says. “I advise my patients who are still worried about sunscreen safety to stick with the simple mineral sunscreens. They should also stay out of the sun during peak hours and wear protective clothing.”

Sunscreen should be applied liberally and reapplied every two hours. It’s important to keep in mind that sunscreen is just one way to protect your skin from the sun.

“I think the biggest danger of using sunscreen use may be the false sense of security it provides”, says George “Just because you use sunscreen doesn’t mean you can’t get sunburned or get skin cancer. Those who use it tend to be in the sun more, and we all tend to under apply sunscreen,” George says. 

How to choose a sunscreen

When looking for a sunscreen, be sure to choose one that:

• provides SPF 30 or higher
• has broad-spectrum protection (protects against both UVA and UVB rays)
• is water-resistant

“There are so many different options for sunscreens nowadays that there’s one out there for everyone,” George says. She recommends trying out different products and finding one you like best. “The best sunscreen is the one you’ll wear regularly.” 

Request an appointment at MD Anderson's Lyda Hill Cancer Prevention Center online or call 877-632-6789.