nausea and vomiting are not diseases, but rather are symptoms of many different condition, such as infection ("stomach flu"), food poisoning, motion sickness ,overeating, blocked intestine, illness, concussion or brain injury, appendicitis, and migraines.Nausea and vomiting can sometimes by symptoms of more serious diseases such as heart attacks, kidney or liver disorders, central nervous system disorders, brain tumors, and some from of cancer.