The tricky part about the UV Sense is that if people are supposed to wear it 24/7, it has to look good and feel comfortable. We spoke to the team behind this micro wearable to see how they managed ...

L’Oreal released its first UV-tracking patch in 2016. It was the size of a Band-aid. It turned from white to blue over time, and to track exact UV exposure, you had to photograph it with your phone.