When a child faints or passes out -- what could be the cause?

Last night, my mom was fixing a long-sleeved sweater of mine I had on. All of the sudden, I got very hot and told her I was going to throw up. I yanked the sweater off (I had just a tank top underneath, not like another long-sleeve shirt)and ran to the bathroom as fast as I could, which was not easy. I kept blacking out and I was stumbling into the walls. I finally got into the bathroom and leaned over the toilet. My mom was running after me because she heard my loud thuds against the walls. She helped me get down on my knees and opened the door (which leads outside) so the cold air was blowing in. She was asking me if I was OK and called my dad to get me a cold washcloth. "I can't hear you!" I said (I think I was hyperventilating a little). "It sounds like you're talking through a walkie-talkie." The room was still spinning, but the cold 30 degree air was definitely helping. My mom was telling my dad how white I was. Eventually, about five minutes later, I was well enough to walk into the living room and lay down on the floor underneath the fan. About thirty minutes later, I was completely fine, no nausea or anything. It was the first time that had ever happened to me. I have experienced nausea/near throwing up experiences if I don't eat breakfast. I am a average, but more on the small size thirteen year old, and I'm very healthy. At the time, we were also watching the news, but it was boring stuff. I do not like having my own blood drawn, but I've seen the birth of my brother as well as my other brother's gunshot wound without feeling sick or faint. It was only about 10:30 at night when I "fainted". Any ideas/suggestions?

I’m 15 years old and I am a triplet. I am a girl with 2 brothers of which all of us are altar servers. I have never fainted while serving while one of my brothers has twice. One time in august and just yesterday, the 30th of November. My other brother has never fainted either. I’m very worried because I find it strange that he has fainted only in church & no where else. Also, he doesn't have low/high blood pressure or anything, hes very healthy. The first time he fainted, we took him to the emergency room, they ran all these tests and of course there was nothing wrong. But we did have to take him to get two root canals and his teeth bonds because he managed to break/ crack his two front teeth. The first time he fainted, he was standing up and all the sudden he fell and hit his mouth on the stairs.
The second time he fainted, yesterday, he was kneeling down on the stairs while the priest was preparing communion and all the sudden he fell back and hit the back of his head/neck. I was so terrified i ran over and was the first one at his aid. His eyes were open yet he was asleep. i managed not to cry as much as the last experience but immediately after the incident we left the church and decided not to take him to the ER. When we got in the car he complained about his vision being spotty and had a major headache. Then he began to throw up. He had a CAT scan and found nothing wrong with him.

My ten yr old grandchild has done this 2 times both times she was worried had a clicks sound then passing out but it not very long she's overwght does someone hv one similar

Saturday November 11, 2014

Yesterday I was in a basketball practice and I was resting against the wall and suddenly I wanted to vomit and I was sweating a lot I also started to get a blackout so I couldn't get my coach so I just stayed were I was. Later I woke up on the floor with my friends around me and my coach with a cotton ball that's when he told me I had fainted. They called my parents and the ambulance, when the ambulance got there they said that since I was standing strait my bones didn't let the blood flow trough my knees and made my blood pressure go down and that was the cause of me fainting.
I hope this helped you by the way my daughter is 11 years old

I had fainting when I was a teenager, it was caused from Anemia which is an Iron deficiency. I also had this because my heart is slower than average which is find and does not cause issues but it can cause dizziness and fainting as well. If you have anemia, your blood does not carry enough oxygen to the rest of your body which can result in fainting. Hopefully this helps.

my son is 13 and has started passing out first time he was unresponsive for 1 hour 45 mins and again today for twenty mins he was brought home in an ambo !! the doctors said first time they got no idea reckon his heart is ok !! but the worry and fear is trying to break myn!!!!