headaches after excercise

If I work out very hard, especially running or circuit-style classes, I always get crippling headaches and a little nausea, and it bears no relation to hydration levels. Sometimes it also feel like the glands in my neck are swollen, like I'm coming down with something.

I believe in my case it has a lot to do with overheating, as I feel I have a temperature just before the headache hits and it often follows going very red in the face. Also even if you don't suffer form high blood pressure, your blood pressure elevates a lot when you exercise hard, and iy coming back down to normal could bring it on.

So long as you have no underlying conditions, exercise headaches can be treated with the same OTC painkillers you'd use for everyday headaches.

Do you think it might have anything to do with your breathing during exercise, perhaps low oxygen levels? Another possible cause may be your blood glucose going low during exercise, low blood glucose can result in a headache later on. Just a couple of things to consider in addition to the water and electrolyte suggestions already made.