How can you tell if someone has a concussion

It's different for everyone. I've had both a mild and a severe concussion in the past. Mild ones usually aren't bad or anything to worry about, but the severe ones are because you can have head trauma of some types. Some usual signs of concussion are going unconscious during the head injury, severe headaches/migraines, sound and or light sensitivity, any wounds or bleeding to head, nausea and vomiting, and having trouble staying awake after the initial head injury. If you or someone you know has hit their head on something and you're worried about whether there's a concussion or not then it's always a good idea to go to the ER and get checked out.