Anosmia is the absence or impairment of the sense of smell. 7% of the people in India suffer from impaired sense of smell. It can be partial or complete.

Anosmia occurs from either an obstruction in the nose or nerve damage. An obstruction prevents odors from reaching the delicate nerve fibers of the nose. They could be caused due to natural aging process or most commonly due to common cold. They can also follow a head injury or an acute or chronic attack of allergies. Many medications may change or decrease the ability to detect odors. The sense of smell is often lost with disorders like tumours, nasal sinus or surgery of the brain. It may also be due to zinc deficiency. Tobacco smoking is the most concentrated form of pollution that most people will ever be exposed to. It impairs the ability to identify odors. Hormonal disturbances or dental problems are also a cause. Anosmia can occur as a part of other loss of function of the brain.

In order to understand the cause of the problem it is important to obtain a careful history of complaints and an examination of the head and neck, a CT scan and skull x-rays. Specific quantitative measurements of smell function need to be performed. Sinus transillumination is a test in which a light is placed against the face to help determine if the sinus are filled with fluid. Scientists have also developed an easily administered "scratch-and-sniff" test to evaluate the sense of smell.

Loss of the sense of smell may be temporary, and ability to smell may return spontaneously, especially after colds or viral infections. Treatment of underlying disorders may correct loss of the sense of smell. Antihistamines are to be taken if the condition is related to allergy. Quitting smoking improves the smell function. Surgical correction of physical blockages and avoid excessive use of nasal decongestants also help. Zinc supplements are sometimes recommended.