Anosmia

Anosmia, or smell blindness, is the inability to detect one or more odors. This condition can be either temporary or permanent, and it is distinct from hyposmia, which involves a reduced sensitivity to some or all smells. Anosmia is divided into two main types: acquired anosmia, which appears later in life due to factors like upper respiratory infections, head trauma, or neurodegenerative diseases, and congenital anosmia, which is present from birth and usually stems from genetic issues or developmental problems in the olfactory system.

The effects of anosmia can be harmful. People who suddenly lose their sense of smell may find food less appealing, though those born without it rarely complain about this and do not report weight loss. The inability to smell can be dangerous, as it prevents detection of gas leaks, fires, chemical spills, noxious fumes, and spoiled food. Misconceptions that anosmia is trivial, along with a lack of awareness about congenital cases, can make it harder for patients to receive the same level of medical support as those who lose hearing or sight. This is significant because scent detection assistance animals are not commonly trained in public programs like guide dogs are for the blind or deaf. Many individuals experience a loss of smell in only one nostril, often from minor head trauma, which is typically only detected when each nostril is tested separately. Losing a sentimental smell memory—such as the scent of grass, a grandparent's attic, a loved one, or oneself—can lead to feelings of depression. Loss of smell may also reduce libido, though this usually does not apply to those with congenital anosmia. Some people with congenital anosmia or early childhood onset report that as children they pretended to be able to smell for various reasons: they thought smelling was a skill for older people, they did not understand the concept but wanted to fit in, they misinterpreted information about scents, or they believed it was a trainable skill like that of a detection dog. As these children grow older, they often realize and report their lack of smell to parents, sometimes to the parents' surprise. Some children try to inform adults early on, but not all are believed, and a parent's response can shape how the child views the condition, including whether they disclose it again.