Whether or not the sense of smell can be restored after several years depends on the cause and degree of the disease. If it is due to atrophic rhinitis, craniocerebral trauma and other reasons for the loss of sense of smell is generally more difficult to recover; if it is due to nasal polyps, sinusitis and other reasons for the loss of sense of smell may be restored. 1. Atrophic rhinitis: the patient’s olfactory loss is mostly due to the atrophy of the mucosa in the olfactory region without gland secretion, unable to dissolve the odor-containing molecules that reach the olfactory region in order to stimulate the olfactory nerve, or the olfactory nerve itself atrophic. At this time, the course of the disease is long, even after treatment can not be reversed, so the loss of sense of smell due to this condition for several years generally can not be restored. 2. Craniocerebral trauma: If the patient suffers from olfactory loss due to craniocerebral trauma which causes the olfactory nerve and olfactory filaments of the sieve plate to be torn or the olfactory bulb to be shredded, the damage to the nerves is irreversible and cannot be repaired, therefore, olfactory loss due to this condition cannot be recovered in a few years. 3. Nasal polyps, sinusitis: If there are nasal polyps in the olfactory region or inflammation in the sinuses, affecting the function of the olfactory region and blocking the pathway for odor molecules to function, the sense of smell can be restored after surgical excision of the nasal polyps or sinus surgery to remove the obstruction, so the sense of smell due to the loss of smell for several years may be restored. When the sense of smell fails for several years, it is recommended to pay attention to it as soon as possible, actively seek medical treatment, make a clear diagnosis, and follow the doctor’s instructions to standardize the treatment.