How do the disease-causing germs invade my body?

Your skin is a wonderful protective barrier that prevents many of the disease-causing germs that you run into each day from entering your body. Only when you have an opening in your skin—like a cut or a scrape—are germs likely to enter there. Most germs enter through your mouth and nose, making their way farther into your body through your respiratory or digestive tracts. But even then, certain chemicals in body tissues and fluids keep many harmful germs from causing problems.