Today, sunscreens have a lot of information on their labels - meant to make sure you buy the right product to keep your skin protected from the sun's UV rays. Understanding the SPF is only part of what you need to know. Sunscreens also provide information on whether they work while you are sweating or in the water and how long they work.
Several years ago, many sunscreens put the word, "waterproof," on the label, implying that you could go swimming without worrying about reapplying sunscreen. With the changes that went into law in the summer of 2012, manufacturers are no longer allowed to use the words, waterproof or sweatproof. The U.S. Food and Drug Administration (FDA), which regulates the sunscreen industry, believed that these words "overstated the effectiveness."
Sunscreens, however, can be "water-resistant." All sunscreens that are marketed as water-resistant must have a rating of 40 or 80. This rating indicates how long the sunscreen remains effective while you are swimming or sweating. That means that after 40 or 80 minutes of swimming or sweating, you should reapply sunscreen. Sunscreens that have a water rating of 80 might state they are "Very water-resistant."
This can be confusing because sunscreen labels also indicate you should reapply sunscreen every two hours. This guideline, however, is meant for dry use. For example, suppose your sunscreen is freshly applied and you are ready to go outside at noon. It states you should reapply every two hours so you believe you are fine until 2:00 P.M. But, you decide instead to go swimming. That means, if you are using a water resistant rating of 40 sunscreen, at 12:40 P.M. you need to reapply your sunscreen in order to stay fully protected from the sun, even though it hasn't yet been two hours. .
For sunscreens that are not water-resistant, the container must include a disclaimer stating that you should use a water-resistant sunscreen if swimming or sweating.
When getting ready to spend time in the sun, choose the sunscreen that best protects you based on your activities for the day. Remember, there isn't any harm in wearing a water-resistant sunscreen on days you aren't planning on swimming or sweating but it can be harmful to wear sunscreens without water-resistance when you are going to be in the water.
It is recommended that you always (year round) wear a sunscreen with at least an SPF of 15 and one that is a broad-spectrum sunscreen, which means it protects you from both UVA and UVB rays.
"Facts About Sunscreen," 2006, Staff Writer, American Melanoma Foundation
"FDA Sheds Light on Sunscreens," Updated 2012, May 17, Staff Writer, U.S. Food and Drug Administration
"Questions and Answers: FDA Announces New Requirements for Over-the-Counter Sunscreen Products Marketed in the U.S.," Updated 2011, June 23, Staff Writer, U.S. Food and Drug Administration