Nose ventilation can not smell may be allergic rhinitis, upper respiratory tract infection, olfactory nerve dysfunction and other reasons. 1. Allergic rhinitis: contact with pollen, dust, dander, hair, willow, seafood and other allergens stimulation, induced allergic reaction of the nasal mucosa, resulting in nasal mucosa on the olfactory cell dysfunction, so the nose will be ventilated smell. 2. Upper respiratory tract infection: viral infection of the upper respiratory tract mucosa, causing specific immune response, resulting in local inflammatory exudate, hemorrhage and other lesions, affecting the function of olfactory cells, so the nose will not be able to ventilate the smell. 3. Olfactory nerve dysfunction: abnormal development of the olfactory nerve in embryonic period, meningioma and traumatic brain injury, etc. lead to olfactory nerve compression damage, multiple sclerosis involving the olfactory nerve and other conditions lead to olfactory nerve dysfunction, the sense of smell can’t be transmitted to the center, and the nose can’t smell the smell of the ventilation. The inability to smell may be related to a variety of factors, it is recommended to consult a doctor for a definitive diagnosis.