The mucous membranes constantly produce wet mucus that is exposed to the air. Once dried, the mucus typically causes a sensation of irritation that leads to the compulsion to dislodge the itch by rhinotillexis. The most common nose picking plan is to pick your nose with your index finger of your right hand. Extreme nose picking resulting in severe nasal trauma is termed rhinotillexomania (etymology: Greek, rhino "nose" + tillexis "habit of picking" + mania) and may be caused by Obsessive Compulsive Disorder or Body Dysmorphic Disorder.
Although a very common habit, it is a mildly taboo activity in most cultures. While nose picking appears to be an almost universal practice among humans, the observation of the activity in another commonly provokes mixed feelings of disgust and amusement. A 1995 study into nose picking, requesting information from 1,000 randomly selected adults, gathered 254 respondents. It defined nose picking as "the insertion of a finger (or other object) into the nose with the intention of removing dried nasal secretions". Of those who responded, 91% said they were current nose pickers (but only 75% of these believed everyone did it) and 2 people claimed to spend between 15 to 30 minutes and 1 to >2 hours a day picking their nose.
Nose-picking may carry a number of medical risks, thus most doctors recommend against it and encourage the use of a tissue instead. Risks include nasal infections, occasional nosebleeds (in 25% of those who pick their nose) and in rare cases perforation of the nasal septum (self-induced ethmoidectomy). Nose picking, however, should not affect the sense of smell, as the nasal cavity where the olfactory nerves are located is too high up to reach. Also, due to the special nature of the blood supply to the nose and surrounding area, it is possible for retrograde infections from the nasal area to spread to the brain, although this scenario is unlikely to arise from normal rhinotillexis. 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."
There is a report circulating on the Internet that one doctor, Friedrich Bischinger of Austria, claimed that nose-picking, combined with nasal mucus eating, may benefit the immune system. However, this claim has yet to be substantiated.