The term “UV index” is not top of mind for most of us — unless you’re a tween or teen girl in 2024. On TikTok, nearly a quarter-million posts use the tag #uv. In many cases, these videos refer to the UV index, a shorthand for a measure of how intense ultraviolet radiation is at a given location. While 3 to 5 is “moderate” and some sun-safety precautions are recommended; 6 through 11 and above are considered “high,” “very high” or “extreme.” Yet many teens are tracking the UV index and going out to tan when the figure gets into dangerous territory. “I don’t know who started using this index for evil, but it seems like that’s catching on right now,” said Brooke Jeffy, a dermatologist in Scottsdale, Ariz. So how can parents or caregivers speak to teens about this? Head to the link in our bio for advice from experts.