If sneezing occurs without any other abnormal sensation, it is not considered to be caused by cancer. The nerve endings in the nasal cavity are stimulated by various causes, which can cause sneezing reflexively. When you inhale irritating gases, the local mucous membrane is stimulated and sneezing occurs. This symptom is also easily caused at the beginning of a cold or when you have allergic rhinitis. You should pay attention to your diet and rest, drink plenty of water to prevent colds, and try not to touch irritating gases. If this symptom occurs frequently, you need to go to the ear, nose and throat for a checkup. It may be caused by local inhalation or chronic inflammatory stimulation, and needs to be treated actively under the guidance of a doctor according to the test results.