When germs get inside your body, they can multiply and cause an infection. Your body's immune system fights off the germs with special cells. It can become a full-on fight against the nasty invaders – and you won't feel better until your body wins! Sometimes when you get sick, it's because you have some kind of infection. If your body's having a little trouble fighting the infection by itself, your doctor may prescribe medicine like antibiotics to help, so just sit back, get some rest, and let your body do the work!