Reverse sneezing (also calle backwards sneezing) or inspiratory paroxysmal respiration is a phenomenon observed in dogs, particularly in those with brachycephalic skulls. Its exact cause is unknown but may be due to nasal, pharyngeal, or sinus irriation (such as an allergy) or the dog's attempt to remove mucus. It is characterized by rapid and repeated forced inhalation through the nose, accompanied by snorting or gagging sounds. It is alarming to the owner and may be distressing to the dog, but is not known to be harmful to the animal. Most dogs are completely normal before and after episodes. In addition most dogs will have repeat episodes of it during their lives.