Sneezing, or sternutation, is a strong, sudden, uncontrolled burst of air through the nose and mouth. Sneezing is caused by an irritation to the nasal lining or the throat.Usually, sneezing is the result of dust or an allergen entering the nose.While sneezing is often annoying, it is usually not serious.It may occur as part of an allergic reaction or may accompany an infection or illness.neezing is caused by an irritation to the nasal lining or the throat. Usually, sneezing is the result of dust or an allergen entering the nose. While sneezing is often annoying, it is usually not serious.