A Spitting Image of Health

How saliva can help doctors diagnose disease

Rinse and spit.

Peter Dazeley/Getty Images

SALIVA’S SOURCE Glands on the bottom of the mouth and sides of the cheeks make saliva and empty it into the mouth via ducts. Within the glands, networks of capillaries take up proteins and other molecules from the blood, adding them to the gland-derived fluid.