The parents of Katelyn Thornley have probably stopped saying "Bless you." Not because they're impolite, but because it would almost as exhausting as the ordeal their 12-year-old daughter is enduring.

Sneezing helps get rid of germs, irritants, and allergens from the nose. Hay fever, respiratory illnesses, and air pollutants may all cause sneezing. Sneezing is a normal function of the body and ...