Anosmia refers to a total loss of smell. It can be congenital, present from birth, or acquired. With multiple causes, this smell disorder can have many consequences in everyday life.

Anosmia is a smell disorder that results in the absence or total loss of smell. It is usually bilateral but can sometimes involve only one nostril. Anosmia should not be confused with hyposmia which is a decrease in smell.

Anosmia can have several origins. Depending on the case, the loss of smell is the consequence:

• an congenital anomaly, present from birth;
• or acquired disorder.

The case of congenital anosmia

In some rare cases, anosmia is present from birth. According to current scientific data, it is a symptom of Kallmann syndrome, a genetic disease of embryonic development.

The case of acquired anosmia

In the majority of cases, anosmia is due to an acquired disorder. Loss of smell can be linked to:

• obstruction of the nasal passages, which prevents the perception of odors;
• an alteration of the olfactory nerve, which disrupts the transmission of olfactory information.

Obstruction of the nasal cavity can occur in different cases such as:

• rhinitis, an inflammation of the mucous membrane of the nasal cavities which can have several origins, in particular an allergic origin (allergic rhinitis);
• sinusitis, an inflammation of the mucous membranes lining the sinuses, the chronic form of which is more often the cause of anosmia;
• nasal polyposis, that is, the formation of polyps (growths) in the mucous membranes;
• a deviation of the nasal septum.

The olfactory nerve can be damaged by:

• smoking;
• poisoning;
• certain drug treatments;
• certain infections, especially those caused by the influenza virus (the flu) or those caused by the herpes simplex virus;
• viral hepatitis, inflammation of the liver caused by a virus;
• head trauma;
• meningiomas, tumors, often benign, which develop in the meninges, membranes covering the brain and the spinal cord;
• neurological diseases.

The course and consequences of anosmia vary from case to case. This smell disorder can be temporary when it is due to a transient obstruction of the nasal passages. This is particularly the case with rhinitis.

In some cases, this smell disorder persists over time, which can affect the daily life of anosmics. Persistent or definitive anosmia can in particular cause:

• a feeling of unease, which can, in the most serious cases, lead to a withdrawal into oneself and a depressive syndrome;
• eating disorders, which can be associated with ageusia, loss of taste;
• a security problem, which is due to the inability to detect warning signs such as a smell of smoke;
• a poor lifestyle, which is linked to the inability to detect bad odors.

Treatment consists of treating the origin of the anosmia. Depending on the diagnosis, several medical treatments may be considered:

• drug treatment, especially in the event of inflammation of the respiratory tract;
• a surgery, especially when a tumor is detected;
• follow-up by a psychotherapist, when anosmia causes psychological complications.