Anosmia is the partial or complete loss of the sense of smell. This loss may be temporary or permanent. Common conditions that irritate the nose’s lining, such as allergies or a cold, can lead to temporary anosmia.
More serious conditions that affect the brain or nerves, such as brain tumors or head trauma, can cause permanent loss of smell. Old age sometimes causes anosmia.
Anosmia usually isn’t serious, but it can have a profound effect on a person’s quality of life.
People with anosmia may not be able to fully taste foods and may lose interest in eating. This can lead to weight loss or malnutrition. Anosmia can also lead to depression because it may impair one’s ability to smell or taste pleasurable foods.
Anosmia is frequently caused by a swelling or blockage in the nose that prevents odors from getting to the top of the nose. Anosmia is sometimes caused by a problem with the system that sends signals from the nose to the brain.
Below are the main causes of anosmia:
Irritation to the mucus membranes lining the nose
This can result from:
- sinus infections
- common colds
- the flu, or influenza
- allergies (allergic rhinitis)
- chronic congestion not related to allergies (nonallergic rhinitis)
A cold is the most common cause of partial and temporary loss of smell. In these cases, the anosmia will go away on its own.
Blockage of the nasal passages
Loss of smell can occur if something is physically blocking the passage of air into the nose. This may include:
- nasal polyps
- bone deformities inside the nose or a nasal septum
Brain or nerve damage
There are receptors inside the nose that send information through nerves to the brain. Anosmia can occur if any part of this pathway is damaged. There are many conditions that can cause this damage, including:
- old age
- Alzheimer’s disease
- brain tumors
- Huntington’s disease
- hormonal problems
- underactive thyroid
- medications, including some antibiotics and high blood pressure medications
- multiple sclerosis
- Parkinson’s disease
- exposure to chemicals that burn the inside of your nose
- brain or head injury
- brain surgery
- malnutrition and vitamin deficiencies
- radiation therapy
- long-term alcoholism
In rare cases, people are born without a sense of smell due to a genetic condition. This is called congenital anosmia.
The loss of smell is difficult to measure. Your doctor may ask you some questions about your current symptoms, examine your nose, perform a complete physical examination, and ask about your health history.
They may ask questions about when the problem started, if all or only some types of odors are affected, and whether or not you can taste food. Depending on your answers, your doctor may also perform one or more of the following tests:
People with anosmia may lose interest in food and eating, leading to malnutrition and weight loss.
People with anosmia should make sure to have functioning smoke alarms in their homes at all times. They should also be cautious with food storage and the use of natural gas because they may have trouble detecting spoiled foods and gas leaks.
Recommended precautions include:
- properly labeling foods with expiration dates
- reading labels on chemicals like kitchen cleaners and insecticides
- using electric appliances
Treatment depends on the cause. If the loss of smell occurs with a cold, allergy, or sinus infection, it typically will clear up on its own in a few days. You should consult your doctor if the anosmia doesn’t clear up once the cold or allergy symptoms have subsided.
Treatments that may help resolve anosmia caused by nasal irritation include:
- steroid nasal sprays
- antibiotics, for bacterial infections
- reducing exposure to nasal irritants and allergens
- cessation of smoking
Loss of smell caused by nasal obstruction can be treated by removing whatever is obstructing your nasal passage. This removal may involve a procedure to remove nasal polyps, straighten the nasal septum, or clear out the sinuses.
Older people are more susceptible to losing their sense of smell permanently.
There is no treatment currently available for people with congenital anosmia.
People with a partial loss of their sense of smell can add concentrated flavoring agents to food to improve their enjoyment.