Blackouts: fainting fear

I was using the cross trainer at the gym and I developed a strange feeling. The next thing I knew I was on the floor. My friends said that I was foaming at the mouth and that my head jerked back when I was on the ground. I also wet myself. I was only unconscious for about a minute, and within half an hour I was back to normal. I've never had anything like this before.

Dr Fred Kavalier answers your health question:

A sudden blackout is always frightening. Sometimes the explanation is obvious. Being squashed in a hot Underground train for an hour is enough to make many healthy people feel dizzy. If the problem goes on for too long, some of these people will pass out. This is a simple faint, which is caused by the blood pressure dropping and the blood supply to the brain being inadequate. As soon as someone faints and falls to the floor, blood rushes to their brain and they quickly wake up. What happened to you, however, sounds much more like a convulsion than a simple faint. A convulsion is caused by unusual electrical activity in the brain, which usually leads to loss of consciousness. The fact that your head jerked back and that you passed urine are also typical of a convulsion. You should not ignore what has happened, as it could happen again with serious consequences. You need to be seen by a neurologist for a thorough examination. If you hold a driving licence you should inform the DVLA about your blackout.

Please mail your questions for Dr Fred to health@independent.co.uk. He regrets that he is unable to respond personally to questions.