The nose has an area of specialised cells which are responsible for smelling (part of the olfactory system). Another function of the nose is the conditioning of inhaled air, warming it and making it more humid. Hairs inside the nose prevent large particles from entering the lungs. Sneezing is usually caused by foreign particles irritating the nasal mucosa, but can more rarely be caused by sudden exposure to bright light (called the photic sneeze reflex) or touching the external auditory canal. Sneezing is a means of transmitting infections because it creates aerosols in which the droplets can harbour microbes.
Nose-picking is a common, mildly taboo habit. Medical risks include the spread of infections, nosebleeds and rarely self-induced perforation of the nasal septum. Nose fetishism (or nasophilia) is the sexual fetish (or paraphilia) for the nose. The psychiatric condition of extreme nose picking is termed rhinotillexomania.
Trauma of the nose (for example, during vaginal delivery) can result in a nasal fracture or nasal septum deviation. The nose is a common site of foreign bodies. The nose is susceptible to frostbite. Nasal flaring is a sign of respiratory distress that involves widening of the nostrils on inspiration.
Because of the special nature of the blood supply to the human nose and surrounding area, it is possible for retrograde infections from the nasal area to spread to the brain. For this reason, the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla, is known to doctors as the danger triangle of the face.
Specific systemic diseases, infections or other conditions that may result in destruction of part of the nose (for example, the nasal bridge, or nasal septal perforation) are rhinophyma, skin cancer (for example, basal cell carcinoma), Wegener's granulomatosis, systemic lupus erythematosus, rheumatoid arthritis, tuberculosis, syphillis, leprosy and exposure to cocaine, chromium or toxins. The nose may be stimulated to grow in acromegaly.
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