Hi My son tends to experience headache and seeing purple when he is exercising or doing work in the hot sun. There was once he cycled in hot weather and when he started seeing purple, he stopped cycling, sat down and felt like passing out but said he could control it. If he drinks some isotonic drinks before cycling, he won t experience this. As for doing work in the hot sun, he would experience seeing purple and a bad headache. I d appreciate your comments and advice. Thank you.
Hi.... by what you quote I feel that your son is experiencing heat exhaustion very fast. This occurs when the fluid in the body gets evaporated very fast due to high ambient temperature like what you have described.  At the same time when he has plenty of fluids and does the same work again he is not experiencing those symptoms, this means that he should HY Chat Doctor.  But I suggest an evaluation by a physician. ...regarding this heat exhaustion. Regards -