Can sunscreen go bad in heat?

Can sunscreen be left in a hot car?

A hot car is not a suitable storage place for sunscreen. Bring the bottle with you rather than keeping a spare there, even if the glove compartment seems keen to expand into skincare. The same storage rule applies wherever temperatures become high, not just inside a vehicle. If you discover a bottle has been left in extreme heat, replacing it is the cautious choice rather than relying on its original protection.1

How should I store sunscreen?

Protect the container from excessive heat and direct sun, including while you are outdoors using it. Sunscreen protects skin from UV rays, which does not make its bottle a sunbathing accessory.2

• At home, choose a storage spot away from direct sunlight and places that become hot.
• At the beach or during outdoor activities, keep the bottle in the shade.
• Wrap the container in a towel to protect it from direct sun when you are outside in the heat for long periods.
• Read the storage instructions on your own sunscreen label and follow them.

Does heat make sunscreen less effective?

Exposure to extreme heat can reduce sunscreen's effectiveness. The concern is the protection you get when you use the product, not simply whether the cream still comes out of the tube, which would be an unusually generous definition of working. The SPF number describes sunburn protection. A higher SPF is not a substitute for following the storage directions.12

When should I replace the bottle?

Replace sunscreen if its color, consistency or smell has changed. Check the expiry date too, and discard a product that has passed it. For a US sunscreen without an expiry date, consider it expired three years after purchase. If you do not know how old the bottle is, discard it. Canadian sunscreens have expiry dates, so check the date on the container rather than applying the US rule to every bottle.123

How to use your replacement in hot weather

1. 1Choose a broad spectrum sunscreen with SPF 30 or higher. Broad spectrum means protection against both UVA and UVB rays. Choose water resistance if you will be swimming or sweating.
2. 2Apply sunscreen generously and evenly to dry, exposed skin 15 minutes before going outdoors. Most adults need about one ounce to cover skin not covered by clothing; body size and exposed area affect the amount needed.
3. 3Cover easy to miss areas, including your ears, neck, tops of your feet and exposed scalp.
4. 4Reapply approximately every two hours outdoors, and after swimming or sweating, following the bottle's directions. Water resistant sunscreen still needs reapplication.
5. 5After applying, return the bottle to shade rather than leaving it beside you in direct sun.

Use shade and protective clothing alongside sunscreen; sunscreen alone cannot fully protect you. If your replacement is a spray, do not apply it near heat or an open flame, and never spray it around your face or mouth. Read the label because directions differ between sunscreen forms.24

If replacing the bottle means trying a new sunscreen and you have sensitive skin, test a small area on your inner forearm and check for a reaction after 48 hours. If a rash or itching develops, try another sunscreen. Speak to a health care provider if you have concerns about the reaction.1