Sense of smell is often seen in colds, chronic rhinitis, sinusitis and so on. 1. Cold and flu: due to the stimulation of pathogens, such as viruses or bacteria on the nasal mucosa caused by stimulation, resulting in congestion and swelling of the nasal mucosa, the nose is blocked, thus causing a loss of sense of smell, when the congestion and swelling is a little bit mild, the sense of smell may be restored. 2. Chronic rhinitis: it is a chronic inflammatory disease that occurs in the mucous membrane and submucous layer of the nasal cavity, often manifested as swelling of the nasal mucous membrane, sometimes accompanied by nasal congestion, when the nasal congestion is severe, it may lead to a temporary lack of sense of smell. 3. Sinusitis: an inflammatory disease that occurs in the mucosa of the sinuses, often leading to symptoms such as runny nose, nasal congestion, etc. In the acute stage of the disease, the nasal congestion may be more severe, and the sense of smell may be temporarily lost. The sense of smell is suddenly absent, and may be caused by deviation of the nasal septum, etc. It is recommended to go to the hospital in time to find out the cause of the active treatment.