Does sunscreen become ineffective as it ages?

Yes. Many sunscreens have an expiration date on the bottle, and that should be followed. All sunscreens are developed to remain effective for three years after production. If you’re using enough sunscreen, you should finish an entire bottle of sunscreen before the expiration date.

Most people don’t use enough sunscreen or reapply when they should. You need to apply sunscreen every couple of hours and you need to use an adequate amount.

As dermatologists, we recommend applying one ounce (about two tablespoons) of sunscreen to all exposed areas of the body. And you should reapply every few hours. If you are sweating, swimming or toweling off, you should apply sunscreen more frequently.

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