Experts Warn Sunscreen Can Become Toxic and Ineffective Over Time

As summer approaches, experts caution against using sunscreen left over from previous seasons, highlighting potential health risks. While reusing old sunscreen may seem economical and environmentally friendly, laboratory tests reveal that prolonged use can reduce the effectiveness of UV filters, leaving skin vulnerable to sun damage. Most sunscreens remain stable for about three years when unopened and stored in cool, dry conditions, but manufacturers generally recommend using the product within 12 months after opening, as indicated by the open jar symbol on packaging.

A rigorous study by the French consumer organization Que Choisir tested eight leading sunscreens under extreme summer conditions, including exposure to 40 degrees Celsius heat, cold storage, and artificial UV radiation. Six of the eight products maintained near-full effectiveness after 14 months of varied storage and use. However, the organization warns against using sunscreens containing the filter octocrylene past their expiration after opening, as it can degrade into a toxic compound. Additionally, physical changes such as clumping or unusual odors indicate the sunscreen no longer disperses UV filters evenly, compromising protection.

Que Choisir advises consumers to avoid using the same sunscreen for more than three consecutive summers to prevent unexpected sunburns and skin damage. While there is no immediate chemical danger, expired or degraded sunscreen poses a real risk of insufficient sun protection. Consumers are urged to check expiration dates and product condition before use to ensure safety during sun exposure.