Last week someone at my sports hall had a convulsion (I hope this is the right term; he went unconscious and his body shook heavily, and his veins seemed to enlarge). Fortunately there was a doctor also playing, so he helped him and he got conscious some minutes after that. I saw the doctor laid him on the floor. That's the only thing I could see since he was surrounded by so many people. Half hour later, he was back sitting peacefully on the bench so I went to him and asked if he's alright. He seemed to be very tired and still a bit "blank" (like still in between his conscience), but he managed to nod to me. Since it's my first time seeing something like that, it struck me on some importance such as: 1. What was that? What can cause it? The weather was hot and rather humid. Could it be dehydration? 2. How can we help such a person experiencing this? What can we do for an immediate relief / first aid? Thanks before for any sharing and/or advices.