The 12-year-old says it began two weeks ago when she was recovering from a cold.
Johnson has been to several doctors but, so far no one has been able to help.
Johnson says the only time she stops sneezing is when she sleeps. She now studies at home and has even had to change the way she eats.
One allergist thinks Johnson suffers from an affliction called "machine gun" sneezing. He says it is an extremely rare condition and can be triggered by several things, including allergies, and sinus problems.