As immune cells learn to recognize and ignore your body s own cells, they learn to recognize and destroy antigens. Every substance from a dust mite to the flu virus to one of your own cells carries it s own chemical ID card . Your immune army s soldier cells is a remarkable arsenal of different types of white blood cells that recognizes the enemy. Any invader must pass through your physical barriers of defense first. Your skin effectively shields your body from invaders.
Stomach acid kills most microorganisms ingested in food or drink.
Fluids such as saliva, sweat and germs contain destructive enzymes. Your respiratory system is the most susceptible form of entry to your body. With every breath you take, millions of invaders and pollutants enter your body. Each of us is required to breathe in at least ten thousand liters of air every 24 hours just to maintain life. Each liter is contaminated with exhaust pollutants and microorganism invaders.