Merciful anosmia is a condition in which the person is unaware of a foul smell emanating from his own

nose A nose is a protuberance in vertebrates that houses the nostrils, or nares, which receive and expel air for respiration alongside the mouth. Behind the nose are the olfactory mucosa and the sinuses. Behind the nasal cavity, air next passes th ...

. This condition is seen in

atrophic rhinitis Chronic atrophic rhinitis, or simply atrophic rhinitis, is a chronic inflammation of the nose characterised by atrophy of nasal mucosa, including the glands, turbinate bones and the nerve elements supplying the nose. Chronic atrophic rhinitis ma ...

. In atrophic rhinitis, the

turbinates In anatomy, a nasal concha (), plural conchae (), also called a nasal turbinate or turbinal, is a long, narrow, curled shelf of bone tissue, bone that protrudes into the breathing passage of the nose in humans and various animals. The conchae ar ...

, venous

sinusoids A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...

, seromucinous glands and nerves undergo

atrophy Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations (which can destroy the gene to build up the organ), poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply t ...

, resulting in a foul smelling discharge. As the

nerve fibres An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...

sensing smell are also atrophied, the patient is unable to appreciate the foul smell.

References

Symptoms and signs: Respiratory system Upper respiratory tract diseases {{med-sign-stub