A lot of people save leftover sunscreen for the following summer. But even if the bottle is not empty, the protection may no longer work as well as before.
Researchers and industry experts point to several signs consumers should look for before using old sunscreen again.
Check the packaging
Many sunscreen products feature a small symbol of an open jar with a number on it. The number indicates how many months the product is normally safe to use after opening.
According to the Norwegian industry organization Kosmetikkleverandørenes forening, the labeling is based on tests involving heat, light, and storage conditions.
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The goal is to ensure that the product continues to perform as expected, according to forskning.no.
Smell and color matter
Researchers recommend using your senses before applying old sunscreen.
If the lotion smells different, has changed color, or become lumpy, it should be thrown away.
Berit Granum from the Norwegian Institute of Public Health told forskning.no that such changes may be signs of product degradation or bacterial growth.
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It is also not a good idea to leave sunscreen exposed to high temperatures or direct sunlight for long periods.
Protection may weaken
The biggest risk with old sunscreen is that its UV protection may become weaker, increasing the risk of sun damage.
Senior researcher Ellen Bruzell therefore recommends buying new sunscreen every season, according to forskning.no.
However, if an old bottle is all that is available, she believes that some protection is still better than none — as long as the product still appears normal.
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Sources: Forskning.no.
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