My 21 y/o healthy son was at the barber and began feeling lightheaded and it progressed to severe dizziness. His vision was very blurred and he couldn't hold his head up. he spilled a cup of water that he was given in his lap due to the severity of his dizziness. he began to sweat profusely afterwards and had a headache. I learned from him that this happened once before but he blacked out for a few seconds, falling to the ground. he cannot recall if there are symptoms prior to dizziness.