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What causes loss of sense of smell? 12 possible conditions

What Is Anosmia?

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 is usually not serious. But it can have a profound effect on a person’s quality of life. People with anosmia may not be able fully taste foods. They may lose interest in eating. This can lead to weight loss or malnutrition. People with anosmia may also become depressed because they are not able to smell or taste pleasurable foods.

What Causes Anosmia?

Anosmia is frequently caused by a swelling or blockage in the nose. This can prevent 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. The main causes of anosmia include:

Irritation to the Mucus Membranes Lining the Nose

Irritation to the nose’s lining may result from:

  • sinus infections
  • common colds
  • smoking
  • influenza (the flu)
  • allergies (allergic rhinitis)
  • chronic congestion not related to allergies (nonallergic rhinitis)

A cold is the most common cause for 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:

  • tumors
  • nasal polyps
  • bone deformities inside the nose or a nasal septum that is not straight

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
  • schizophrenia
  • epilepsy
  • diabetes
  • chemical exposures that burn the inside of your nose
  • brain or head injury
  • brain surgery
  • malnutrition
  • radiation therapy
  • long-term alcoholism
  • stroke

Rarely, people are born with no sense of smell because of a genetic condition. This is called congenital anosmia.

How Is Anosmia Diagnosed?

The loss of smell is difficult to measure. A doctor or healthcare provider may ask you some questions about your current symptoms, examine your nose, perform a complete physical examination, and ask about your health history.

He or she 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:

  • computerized tomography (CT) scans, which use X-rays to create a detailed image of the brain
  • magnetic resonance imaging (MRI), which uses radio waves and magnets to view the brain
  • X-ray of the skull
  • nasal endoscopy to look inside your nose

What Are the Complications of Anosmia?

People with anosmia may lose interest in food and eating. This could lead to malnutrition and weight loss.

Patients 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. 

How Is Anosmia Treated?

Treatment depends on the cause. If the loss of smell occurs with a cold, an allergy, or a sinus infection, it will typically clear up on its own in a few days. You should consult your doctor if the anosmia does not clear up once the cold or allergy symptoms have subsided.

Treatments that may help resolve anosmia caused by nasal irritation include:

  • decongestants
  • antihistamines
  • 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 operations to remove nasal polyps, straighten the nasal septum, or clear out the sinuses (NHS, 2012).

Elderly people are more susceptible to losing their sense of smell permanently. There is no treatment available currently for people with congenital anosmia.

Patients with partial loss of their sense of smell can add concentrated flavoring agents to food to improve their enjoyment of the food.

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See a list of possible causes in order from the most common to the least.


Sinus Infections (Sinusitis)

A sinus infection causes the sinuses and nasal passages to become inflamed. Facial swelling is a common sign of this type of infection.

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Enlarged Adenoids

Adenoids are small tissues located at the back of the throat. They are similar to the tonsils, and located right above them. Both adenoids and tonsils are part of the immune system. Adenoids are present at birth, an...

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Nose Injury

Nosebleeds are common and rarely indicate a serious medical problem. However, frequent nosebleeds, a bleed that lasts longer than 20 minutes or occurs after an injury may require medical attention.

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Adult Brain Tumor

A brain tumor is the growth of abnormal cells in your brain. Whether the growth is cancerous or not, any brain tumor is serious. Symptoms can include both cognitive and physical control problems.

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Head Injury

This condition is considered a medical emergency. Urgent care may be required.

A head injury could be an injury to the brain, skull, or scalp. It can vary in severity depending on the cause. In some cases face swelling can be a sign of a head injury.

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Cocaine and related disorders

Cocaine is extracted from the coca plant, which grows in Central and South America. It is processed into many forms for use as an illegal drug of abuse.

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Nutritional Deficiencies (Malnutrition)

A nutritional deficiency occurs when the body doesn't absorb the necessary amount of a nutrient. Deficiencies can lead to a variety of health problems.

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Nasal Polyps

Have you ever felt like you have a cold that never goes away? Nasal congestion that doesn't seem to go away, even with over-the-counter cold or allergy medication, may be caused by nasal polyps.

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Parkinson's Disease

Parkinson's disease (PD) is a progressive neurological disorder. It first presents with problems of movement. Smooth and coordinated muscle movements of the body are made possible by a substance in the brain calle...

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Radiation Therapy

Radiation therapy is a cancer treatment that uses concentrated radiation beams to kill cancer cells. The most common type of radiation therapy is external beam radiation. This type involves a machine that direct...

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What is Alzheimer's Disease?

Alzheimer's disease (AD), the most common cause of dementia, is a progressive brain disorder. Learn about the causes, signs and research being done about AD.

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The thyroid gland produces a hormone that controls how your cells use energy (metabolize). Hypothyroidism occurs when the body doesn't produce enough. Untreated, it can cause complications like obesity and heart disease.

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This feature is for informational purposes only and should not be used to diagnose.
Please consult a healthcare professional if you have health concerns.