The immune system is made up of special cells, proteins, tissues, and organs that defend people against germs and microorganisms.

Find out what the experts have to say.

Find out what the experts have to say.

Find out what the experts have to say.

Dehydration is when the amount of water in the body has dropped too low. Read about what causes dehydration, what it does to your body, and how to prevent it.

Germs are tiny organisms that can cause disease - and they're so small that they can creep into your system without you noticing. Find out how to protect yourself.

Did you know that the most important thing you can do to keep from getting sick is to wash your hands? If you don't wash your hands frequently, you can pick up germs from other sources and then infect yourself.