As with many organs in the human body, the sense of smell also diminishes with age. Since this is a long and slow process, it usually goes unnoticed. However, if the sense of smell suddenly decreases or is distorted, producing a sensation of smell that is not related to taste, it is likely to indicate damage to the olfactory nerve or a brain tumor, and should not be taken lightly. Sinusitis Sinusitis is one of the most common causes of olfactory disorders. Sinus inflammation can cause congestion and swelling of the nasal mucosa or produce large amount of secretion to block the nasal cavity, which in turn causes the air inhaled into the nasal cavity to fail to reach the olfactory receptor area and cause olfactory impairment. In addition, the pathological changes of olfactory mucosa are another important cause of olfactory impairment. Patients with sinusitis produce too many oxygen radicals, which can directly damage the olfactory cells and make the olfactory mucosa atrophy and thinning, resulting in olfactory atrophy or loss. Statistics show that 45.6% of patients with olfactory disorders suffer from sinusitis, and 66% of sinusitis patients have olfactory disorders. Intranasal tumor The olfactory nerve is a sensory nerve. If there is a tumor in the nasal cavity, it can cause nasal obstruction and prevent the smell from reaching the olfactory nerve, resulting in reduced or lost sense of smell. Most nasal tumors present as unilateral loss of sense of smell. Intracranial tumors The sense of smell depends on the nerve in the mucosa of the nasal cavity, which is transmitted from the olfactory nerve to the olfactory center in the brain. If tumors such as meningioma in the olfactory sulcus are present in the brain, the tumor may compress the olfactory center and olfactory nerve, so that the olfactory information cannot be transmitted in or out normally, thus causing olfactory impairment or loss. Trauma About 5-10% of patients with cranial trauma have olfactory impairment, and 1% of children. Although trauma to the nose and brain is not always associated with olfactory disturbance, severe trauma is a common cause of olfactory disturbance, and sometimes even mild trauma can cause loss of smell, depending on the location of the injury. Trauma to the forehead is the most common and is usually due to direct injury to the mucosa of the olfactory area or the olfactory nerve. Oedema and blood clots caused by trauma can also block the nasal cavity and prevent air from reaching the olfactory area through breathing, thus causing olfactory impairment. Viral infections Acute rhinitis caused by respiratory viruses can cause reduced sense of smell due to nasal obstruction, which can mostly return to normal after the nasal blockage is removed. Histological studies also support the theory of viral involvement of the central nervous system, possibly by viral or toxic products affecting the olfactory center, and usually this type of olfactory impairment is difficult to recover. Parkinson’s disease Parkinson’s disease is a disorder characterized by tremor, muscle rigidity and abnormal postural gait. There are about 2 million Parkinson’s patients in China. Studies have found that 70% to 90% of Parkinson’s disease patients have olfactory impairment. Since the nerves on the nasal mucosa perceive odor and then transmit from the olfactory nerve to the olfactory center in the brain, and the lesions in the brain of Parkinson’s patients can affect the olfactory center, so it has an important impact on the olfactory function and manifests as olfactory impairment. Alzheimer’s disease Alzheimer’s disease is a primary degenerative brain disease and is one of the most common neurodegenerative diseases in humans. It has been found that the loss of smell is present in the early stages of Alzheimer’s disease, even earlier than the typical symptoms such as memory loss and mental decline. This is mainly due to the fact that in the process of neurodegenerative disease, Alzheimer’s patients can first affect the olfactory center and cause olfactory impairment. Nutritional deficiencies such as folic acid and vitamin B12 can also cause damage to the nasal mucosa, resulting in decreased sense of smell. Folic acid and vitamin B12 are important coenzymes in the process of DNA synthesis in the cell nucleus, when deficient, they will affect DNA synthesis and lead to stagnation of cell nucleus development. Therefore, once the sense of smell suddenly decreases or is distorted, the above diseases should be ruled out as soon as possible, and then consider adjusting the diet and balancing nutrition. Tips: Early medical treatment is needed for olfactory impairment after body bumps. If you fall or have a minor brain bump, the brain may be shocked, but the tiny olfactory nerve fibers may be partially or completely disconnected and the sense of smell may be reduced or lost. If left untreated, the olfactory nerve may be permanently damaged. Therefore, it is important to seek early medical attention when the sense of smell becomes impaired after physical touch.