Why do we get ill when we get stressed?

When your body is stressed you are constantly in the fight or flight mode. Your heart beat is higher, blood pressure is up and constant alertness is given full attention to your bodies defenses. Ther are a lot of flowing hormones to be able to use all of your strenght and more to survive. When this continues for long periods of time you dont sleep, eat and think properly and your body's immune system is weakened and you get sick easier.