There are many reasons why the nose smells bad, such as nasal foreign body with infection, atrophic rhinitis, sinusitis and so on. 1. Nasal foreign body with infection: when there is a foreign body in the nasal cavity, it can affect the ventilation and drainage of the nasal cavity and sinuses, causing the growth of pathogenic bacteria, triggering purulent secretion, so it leads to smelly nose. 2. Atrophic rhinitis: also known as stinky nose, mainly in the nasal cavity, sinus mucosal epithelial atrophic changes, which can lead to the loss of the nasal cavity of the heating and humidification function. And due to the damage of the nasal mucosa, resulting in impaired immune function, odor nasal bacteria and viruses and other substances are easy to infect the internal mucosa of the nasal cavity, so that the nasal cavity appeared to be a bad smell serious odor. 3. Sinusitis: an inflammatory disease of the sinus mucosa, mainly caused by bacterial, fungal and viral infections and other pathogens, which can lead to inflammatory swelling of the patient’s nasal mucosa and the appearance of purulent secretions, especially odontogenic maxillary sinusitis will have a smell so that there will be a foul odor inside the nose. In addition, nasal tumors, osteomyelitis of the jawbone, nasal foreign bodies, etc., can cause a foul smell inside the nose, so it is best to go to the hospital in time for examination and diagnosis.