NEWS | June 26, 2020

A primer on sun safety from a UC Davis Health expert

What you need to know about sunscreen, UV rays and more


It’s summer, which means UC Davis pediatricians are fielding questions from families about sunscreen, sunburn and how to best protect children from the Sacramento sun.

Sunscreen should be reapplied every two hours, and after getting in the water, toweling dry or sweating. Sunscreen should be reapplied every two hours, and after getting in the water, toweling dry or sweating.

Those questions are important. Skin cancer is actually the most common cancer in the U.S. and worldwide – every year, about 5 million skin cancers are diagnosed in the U.S. But skin cancer is also one of the most preventable cancers, and there’s much that people can do to limit exposure and risk.

“We know that sun exposure and sunburns in childhood multiplies the risk of developing skin cancers as adults. And we know that it’s really important to protect our kids’ skin from harmful UV rays,” said UC Davis pediatrician Samantha Goggin. “Just one blistering sunburn in childhood can double the risk of developing melanoma in later life. Establishing sun safety habits early in life is crucial to minimizing the risk of skin cancer in the future.”

The meaning behind SPF numbers

Proper use of sunscreen is crucial to reducing the risk of sun damage and skin cancer. The SPF, or sun protection factor, measures the sunscreen’s ability to prevent damage from UV rays.

But what specifically do the numbers mean? If you are using SPF 30, it will allow 3% of UV rays into your skin. If you are using SPF 50, it will allow about 2% of those UV rays through. 

Most dermatologists agree that it’s best to us a sunscreen with an SPF of at least 30. It’s also not just the SPF that matters. It’s important to get a sunscreen that is water resistant as well as broad spectrum so it will block both UVA and UVB rays. (UV stands for ultraviolet – a range of  light wavelengths that are not visible to the human eye.) Both UVA and UVB rays are harmful. UVA is associated with skin aging and UBV is associated with burns. 

How to apply sunscreen

While the brand of sunscreen doesn’t matter much, it’s crucial to look at the ingredients. Sunscreen has two main types of ingredients: physical blockers (zinc oxide and titanium dioxide) and chemical blockers (avobenzone, oxybenzone and others). Physical blockers tend to have broader coverage and are effective immediately after being applied. Chemical blockers need to be applied 20 minutes before sun exposure. 

However, physical blockers tend to be very thick and can be more difficult to rub in.  They also rub off easier and need to be applied more frequently.   

Whichever sunscreen you choose, it must be reapplied every two hours and after getting in the water, toweling dry or sweating.

Parents also need to remember to apply an adequate amount of sunscreen, and to apply it frequently. For an adult, an ounce – enough to fill a shot glass – is recommended to cover exposed areas. For kids, it’s about half that amount. When in doubt, use too much.

And don’t miss areas like the ears, feet, ankles or neck. Additionally, if you are using bug spray, put it on after applying sunscreen.

It’s important to remember that no sunscreen is completely effective at filtering out all the UV rays, and that using sunscreen doesn’t mean you are completely protected. Hats, protective clothing and sunglasses are also good ways to limit sun exposure.

Spray versus lotion?

Both spray-on and lotion sunscreens work well if used correctly and with the appropriate amount. However, it can often be difficult to get a good application with the sprays and it’s easy to miss some areas or not apply enough.  

Lotions seem to be a little easier to correctly apply a thick, even coat. One caution about the sprays: They can inadvertently be inhaled and cause irritation in some people. So anyone with asthma or  other sensitivities should avoid sprays and particularly avoid spraying it near the face. It’s safest to spray it into your hands and then apply it to your face.  

What kinds of sunglasses are best?

Eye protection is also really important and commonly overlooked. If possible, choose sunglasses that have 100% UVA and UVB protection. A lot of sunglasses do not have adequate UV protection, so check before buying. 

Polarization is also something that can come with sunglasses. Polarized lenses decrease glare from surfaces, but do nothing to protect from UV rays. 

How old should children be to use sunscreen?

The American Association of Pediatrics recommends starting sunscreen use at 6 months of age. 

Before 6 months, make every effort to prevent any sun exposure to infants. Infants are very vulnerable to the sun, so stay in the shade or use protective clothing that effectively covers all exposed skin.  

The most harmful time of the day

It is also best to avoid being outside when the UV penetration is strongest. That’s when the sun is directly overhead, generally between 10 a.m. and 4 pm.

During this period, it’s important to wear sun-protective clothing. Tightly woven or dark-colored clothing is most helpful to block UV rays.

How to treat sunburns

If your child gets a sunburn, there are a few ways to alleviate some of the discomfort. By far, the most important thing to do is also the obvious one: Get out of the sun right away and minimize any further exposure. The redness associated with a sunburn typically shows up two to six hours after exposure and will peak within about 24 hours. The following are other treatment options:

  • Taking a medication like ibuprofen or other NSAIDS can help reduce the swelling and redness associated with a burn
  • A moisturizer that contains aloe vera can be soothing to the skin.
  • Apply a cool compress to the affected area.
  • Drink plenty of water to prevent dehydration.

“You should see a doctor if your child develops blistering that covers a large part of the body, shows signs of a skin infection – including pus or red streaks leading from the blister – or if the sunburn is accompanied by confusion, high fever, chills or severe dehydration. That might be a sign of heat stroke,” Goggin said.

Related links

Kids Considered podcast episode on sun safety