Yes, sunscreen does expire — and using an old bottle might not protect your skin like you think.

If you’ve ever found yourself with only an old bottle of sunscreen lying around, you might have wondered: Does sunscreen expire?

The Food and Drug Administration (FDA) requires that all sunscreens remain at their full strength for 3 years.

You can look to the expiration date on a bottle of sunscreen to determine how long it will last. The only exception to this is when a manufacturer has proven its product to last at least 3 years.

Once sunscreen has expired, it becomes less effective at blocking UV rays, therefore increasing your risk of sunburn and skin cancer. In addition to this, exposure from direct sunlight and high temperatures can cause sunscreen to become less effective over time.

To determine whether sunscreen has gone bad or not, look to the expiration date stamped on the packaging.

Be sure to discard any unused sunscreen after this date as it may no longer be effective in preventing sunburn.

Since some countries don’t require the use of expiration dates on sunscreen, it’s a good idea to write down the month and year you purchased it (for example, with a marker on the bottle).

Another indicator is any obvious changes, such as how it smells or how it applies to your skin. If the smell or consistency is off, toss it.

Lastly, use your own judgment. For example, if you’ve left a bottle of sunscreen in a hot car for a year, it’s probably gone bad.

Keep sunscreen in good condition by storing it in a cool, dark place. Exposing the container to excessive heat or direct sun can cause its ingredients to become less effective.

When outdoors, you can protect sunscreen by wrapping the bottle in a towel or placing it in the shade. Keep the lid on firmly at all times.

If you’re going to be out in the sun for a long time, you can store sunscreen in a cooler.

According to FDA regulations, sunscreen has a shelf life of 3 years. For the best sun protection, use your sunscreen before the stated expiration date and store it in a cool, dark place.

Most important, discard sunscreen that has any obvious changes in color, smell, or consistency. Remember: When in doubt, throw it out.