New sunscreen stickers alert you when you need to reapply

The stickers react to harmful UV rays, changing color as your sunscreen protection fades.

Sunscreen stickers alert the wearer when their protection has faded.

New technology is making it easier to stay alert and apply the recommended amount of sunscreen when you spend extended amounts of time outdoors. A sticker called SpotmyUV goes directly on the skin and alerts you when your sunscreen is no longer providing sufficient protection against UV rays.

Applying sunscreen is incredibly important for maintaining skin health, but sunscreens break down and fade when they’re exposed to sunlight, so you have to reapply regularly if you’re going to be outside for extended periods of time. Many people don’t do it either because it’s a pain or they just forget.

Check yourself —Sunscreens contain active ingredients that block UV light from penetrating the skin by either absorbing the light and converting it into heat, or by physically reflecting it. But chemical blockers in sunscreen become inactive as they do their job, so one layer before you go outside isn’t going to be enough to get the full benefits. The SpotmyUV sticker is meant to be applied under the sunscreen, and as the sun breaks it down, the sticker begins to change to a purple color, indicating that it’s beginning to get hit with harmful UV rays and you need a fresh layer of sunscreen.

This isn’t the first product of its kind. A company called LogicInk sells a UV-sensing temporary tattoo that works in a similar way.

Nano-technology — Tattoo electronics that attach directly to the skin and monitor biochemical signals, like hydration levels, have become a fast-growing field of research in part because the technology has come down dramatically in cost. Because sensors are getting smaller in size, tattoo-based electronics have the potential to offer real-time monitoring of health signals as a person goes about their day, but without creating discomfort. Stickers with embedded sensors can easily be 3D printed to different shapes and sizes.

The SpotmyUV stickers are available online in 6-packs for $8. Each sticker is good for 12 hours of use, including reapplications of sunscreen.