The nose can not smell, is the sense of smell failure, called very uncomfortable, especially delicious food in front of the eyes, but also can not wait. Then why can’t we smell? The olfactory conduction pathway that can smell We can smell because there is a set of conduction pathway in the brain that specifically manages the sense of smell. Under normal circumstances, odor enters the nasal cavity and reaches the upper part of the nasal septum and the mucosa of the upper turbinate. The mucosa of the turbinate is rich in olfactory cells, and the olfactory cells pass the perceived odor stimulus through the middle part of the anterior cranial base (about 20 or so) into the skull, forming the olfactory nerve and olfactory bulb, and the stimulus is conducted by the olfactory nerve into the pear-shaped lobe of the highest center of the olfactory hemisphere. Through the above conduction, we perceive various kinds of odors. In addition, the olfactory bulb, the lateral olfactory gyrus, is also an important olfactory primary center, which integrates olfactory afferent impulses. The reason for not being able to smell odor is related to the damage of olfactory conduction pathway. 1, caused by nasal diseases Various nasal diseases including cold, chronic sinusitis, rhinitis, nasal polyps, allergic rhinitis, nasal tumor and nasal surgery, chemical irritation, etc., cause olfactory cells or their function to be damaged in the nasal mucosa, so that the smell is not detected. This is the most common reason. 2. Damage to olfactory nerve caused by head trauma, commonly seen in skull base fracture with olfactory nerve damage, resulting in reduced or absent sense of smell. It is also a common cause. 3, Intracranial tumor Such as anterior skull base tumor, especially meningioma compressing the olfactory nerve. 4. Intracranial infection including bacterial infection and viral infection of olfactory nerve and olfactory center, resulting in loss of sense of smell. Various infections cause edema of olfactory cells and nerves, or even stretching of olfactory cells and nerves, resulting in decreased ability of olfactory cells to sense stimuli and decreased conduction function of nerves, which affects the sense of smell. 5, Dementia, Alzheimer’s disease, aging is also one of the causes. 6.Decrease in the number of olfactory cell receptors makes the sense of smell decrease. The cause is unknown and may be related to cell aging and apoptosis. What should I do if I can’t smell? First of all, self-examination for nasal diseases, such as cold, chronic rhinitis, nasal ventilation, etc. Cold symptoms are familiar to everyone, nasal congestion, sneezing, runny nose, fever, cough, etc. If it is confirmed to be a cold, treat the symptoms and most of the olfactory functions can be restored after the cold gets better. If it is chronic rhinitis, sinusitis, etc., you need to go to an ear, nose and throat specialist and easily do not prescribe your own medicine to avoid delaying the condition. Secondly, if you find that your sense of smell has decreased or disappeared for no reason, go to the hospital as soon as possible to have a cranial CT or MRI examination to rule out intracranial tumor disorders. Thirdly, if the head is traumatized and the sense of smell decreases or disappears, consider the olfactory nerve injury and consider hospitalization.