HSHS St. Mary's answers frequently asked questions on sunscreen use.
As we head into summer with more outdoor activities, it is important everyone take steps to prevent sun damage on their skin. According to the Centers for Disease Control and Prevention (CDC), the sun’s ultraviolet (UV) rays can damage skin in as little as 15 minutes.
The National Council on Skin Cancer Prevention has designated the Friday before Memorial Day, May 28, as National Sunscreen Day or to encourage sun safety awareness and to remind everyone to protect their skin while enjoying the outdoors.
Following guidance from the American Academy of Dermatology (AAD) and the CDC, HSHS St. Mary's offers the following answers to some of the most frequently-asked-questions about using sunscreen to stay safe in the sun.
Who should wear sunscreen?
Everyone older than six months of age who will be spending any time outside (ideally, parents should avoid exposing babies younger than six months to the sun’s rays). Sunscreen use can help prevent skin cancer by protecting you from the sun’s harmful UV rays.
Do I only need to put on sunscreen when it is sunny outside?
You should apply sunscreen every day if you will be outside. The sun emits UV rays year-round and even on cloudy days, up to 80% of the sun’s harmful UV rays can penetrate your skin. Being out in the sand, water and even snow increase the need for sunscreen because they reflect the sun’s rays.
What sunscreen should I use?
To protect your skin from sunburn, early skin aging and skin cancer, everyone should use sunscreen that offers the following:
- Broad-spectrum protection that protects against sunlight’s ultraviolet A- and B-rays (UVA and UVB). All sunscreen products protect against UVB rays, which are the main cause of sunburn and skin cancers. But it is important to also protect against UVA rays, which also contribute to skin cancer and premature aging.
- Sun Protection Factor (SPF) 30 or higher.
- Water-resistant (effective for up to 40 minutes in water) or very water-resistant (effective for up to 80 minutes in water). Even when using a water-resistant sunscreen, you should reapply after getting out of the water or sweating.
Is a higher SPF sunscreen better than a lower SPF sunscreen?
Dermatologists recommend using a sunscreen with an SPF of at least 30, which blocks 97% of the sun's UVB rays. Higher-number SPFs block slightly more of the sun's UVB rays, but no sunscreen can block 100% of the sun's UVB rays.
How much sunscreen should I use and how often should I apply it?
The AAD recommends that you apply enough sunscreen to cover all skin that clothing will not cover, approximately one ounce. Don’t forget to:
- Apply to the tops of your feet, your neck, your ears and the top of your head.
- Apply sunscreen to dry skin 15 minutes before going outdoors.
- Protect your lips, apply a lip balm or lipstick that contains sunscreen with an SPF of 30 or higher.
- Reapply sunscreen approximately every two hours, or after swimming, sweating or toweling off, according to the bottle directions.
It is important to note that higher-number SPFs last the same amount of time as lower-number SPFs. A higher-number SPF does not allow you to spend additional time outdoors without reapplying.
Does sunscreen expire? Can I reuse the sunscreen I bought last summer?
Since dermatologists recommend using sunscreen every day when you are outside, not just during the summer, a bottle should not last long. If you find a bottle of sunscreen that you have not used for some time, here are some guidelines from the AAD to follow:
- The FDA requires that all sunscreens retain their original strength for at least three years.
- If the expiration date on your sunscreen bottle has passed, throw out the sunscreen.
- If you buy a sunscreen that does not have an expiration date, write the date you bought the sunscreen on the bottle, so you’ll know to throw it out in three years.
- Look for visible signs the sunscreen may no longer be good, such as any obvious changes in the color or consistency of the product, which means it’s time to purchase a new bottle.
Are there other ways to stay safe in the sun?
In addition to these sunscreen tips, other ways you can protect yourself from UV rays include seeking shade under a tree, umbrella or other shelter, as well as wearing wide brimmed hats, sunglasses and tightly woven clothing or long sleeves and pants.
For more information, visit the American Academy of Dermatology’s Sunscreen Resource Center at