There’s More to Sun Protection than SPF

There’s no shortage of sunscreen options on the market. In fact, by the Environmental Working Group’s count, there are over 1,700 options on shelves in the U.S. today. While their forms may vary from sprays, lotions, and sticks, one thing they all have in common is SPF.

SPF stands for Sun Protection Factor. It is a measure of how well a sunscreen protects your skin from UVB rays, which are responsible for producing sunburn and play a major role in skin cancers. However, SPF does not reflect how well a product protects against UVA rays, which penetrate the skin more deeply than UVB rays, and are associated with skin aging and cancer, such as melanoma.

So, while SPF is important, for the maximum protection, you want to look for products that offer SPF protection from UVB rays, AND “broad-spectrum protection” against UVA rays.

Most dermatologists recommend using a broad-spectrum sunscreen with an SPF of at least 30. This provides good protection for everyday activities. If you're planning a beach day or outdoor adventure, consider bumping up to SPF 50 or higher.

How SPF Works

Think of SPF as your skin's personal bodyguard against UVB rays. Here's what it provides:

An SPF 15 sunscreen blocks about 93% of UVB rays
SPF 30 blocks about 97% of UVB rays
SPF 50 blocks about 98% of UVB rays
SPF 100 blocks about 99% of UVB rays

The difference between SPF 30, 50 and 100 might seem small, but that extra 1-3% can make a big difference. Especially for people who work or spend a lot of time outdoors and those with sensitive skin.

Of course, what is in your sunscreen will not matter if you do not use it correctly. For the best protection:

Use lotions and sticks for the most consistent and complete coverage
Apply sunscreen generously, about 15-30 minutes before sun exposure
Reapply every 2 hours, or more often if you're swimming or sweating
Don't forget commonly missed spots like ears; back of the knees, hands, and neck; and the tops of your feet

Other steps to take to reduce exposure to skin-aging and cancer-causing rays include:

Cover up with long-sleeved shirts, wide-brimmed hats, and long skirts/wraps or pants
Find shade or put up an umbrella or awning to create some
Plan outdoor activities to avoid when the sun’s rays are strongest (between 10 a.m. to 2 p.m.)

One last important point about sunscreens: They do expire.

The FDA requires sunscreens to remain effective for three years.

If you’ve got a stash of old sunscreens, check the expiration date before applying. If you buy sunscreen and it doesn’t have an expiration date, write the month and year of purchase on the container for future reference.

Lixia Ellis, MD, PhD is a board-certified dermatologist at SVMC Dermatology.