It is illegal to wear them in high school for safety reasons.
Yes you can wear a skull cap under a ski helmet.
some where "skull caps" which is like a compression type of material but in high school its a rule that you can't wear anything under your helmet
Nope
Possibly because she's famous?
Wearing a cycling cap under a helmet can provide benefits such as moisture-wicking to keep sweat out of your eyes, sun protection for your head and eyes, and added warmth in cooler weather. Additionally, the brim of the cap can help shield your eyes from sun glare and rain.
Skull cap, like from under armour
Helmets have always had earholes in football.
It keeps the sweat out of their eyes. Football players sweat a lot under those helmets and when they take them off, it will roll into their eyes. Some guys wear the skull caps under their helmets for the same reason, and so that their helmet doesn't pull their hair out when they take it off.
A Du Rag under the helmet underarmour shirt and compression shorts with some hood tube socks
You can wear a thin, snug-fitting sports cap or a headband that can fit comfortably under a horseback riding helmet. Avoid wearing hats with a brim or bulky designs as they may affect the fit and safety of the helmet.
In CA you can. Other states I don't know. In most states you can only get a ticket if you are under the age of 13 and without a bike helmet, but again, this varies between states.
You can, but most players don't. If the helmet is too big, wearing your cap under it is a good way to make it fit better though.