Feet are specifically prone to fungal infections, not specifically legs (for most people). I would also worry about vaginal yeast infections for girls if they constantly wear multiple layers that are closely fitting in that region.
I feel like leggings are so commonly worn these days for sleep, clothes, excersize. . Wouldn’t that material be a really bad choice then.
In fact it is recommended to have kids sleep in fitted pajamas due to fire risk. How does that differ from tights? In terms of vaginal issues.
Is this your own idea or something you heard from a dr regarding the general public?
People in hospitals often wear compression tights to prevent blood clots. I don’t really think it’s a concern unless there is an underlying condition.