Loss of Smell: Causes, Diagnosis & Treatment

Loss of smell is a symptom that can be caused by respiratory infections, such as COVID-19 or the flu. It can also happen when a condition blocks the airways or affects the central nervous system, such as a deviated septum, tumor, or Alzheimer’s disease.

Depending on the cause, loss of smell, which is medically known as anosmia, may occur with other symptoms. These can include headache, fever, cough, memory loss, or even seizures.

It is recommended to see an ENT specialist or general practitioner if loss of smell is not related to a respiratory infection. Medical evaluation is also recommended when loss of smell lasts for a few weeks, even after recovering from a respiratory infection.

What loss of smell can be

The main causes of loss of smell are:

1. COVID-19

COVID-19 is an infection that can cause loss of smell due to an exaggerated immune system response. This response can reduce the number of olfactory neurons, which are the cells in the nose that detect smells.

In addition, COVID-19 can also cause a dry cough, fever, muscle pain, headache, runny nose, and sore throat.

What to do: treatment for mild COVID-19 may include medications prescribed by a doctor, such as fever reducers, pain relievers, or anti-inflammatory drugs. Severe COVID-19 should be treated in the hospital with oxygen and medications given through a vein.

2. Flu and cold

The flu and common cold are illnesses that cause inflammation of the airway lining. This increases mucus production and can lead to symptoms such as a stuffy nose, loss of smell, cough, runny nose, and sore throat.

What to do: medications such as acetaminophen or ibuprofen may be recommended by a doctor to relieve flu symptoms. Drinking plenty of water, resting, and rinsing the nose with saline solution can also help with recovery.

3. Sinusitis

Sinusitis is inflammation of the sinuses, which are located around the nose and eyes. It can cause symptoms such as loss of smell, headache, nasal discharge, and a feeling of pressure in the forehead and cheekbones.

What to do: sinusitis treatment should be guided by a doctor and may include nasal sprays, cold and flu medications, corticosteroids, and oral antibiotics. Some home measures, such as nebulization, drinking warm teas, and drinking plenty of water, can also help relieve sinusitis naturally.

4. Nasal polyp

A nasal polyp is an abnormal growth of tissue inside the nose. It can block smells from reaching the olfactory area, causing loss of smell, as well as other symptoms such as a constant runny nose, a stuffy nose sensation, and persistent headache.

What to do: treatment may involve corticosteroid nasal sprays, such as fluticasone or budesonide, which should be recommended by an ENT specialist. In some cases, the doctor may also recommend surgery to remove the polyps.

5. Head injury

A head injury is an injury to the skull that is usually caused by a strong blow to the head. It can injure the nose or sinuses, blocking the passage of smells, or damage the olfactory areas of the brain, leading to temporary or permanent loss of smell.

In addition, a head injury can also cause loss of consciousness and/or memory, mental confusion, severe headache, seizures, and bleeding from the head or face.

What to do: treatment varies depending on the severity of the trauma. Pain medication, stitches, and/or dressings may be recommended, or surgery may be needed to relieve pressure in the head and control bleeding.

6. Alzheimer’s disease

Alzheimer’s disease is a neurodegenerative disorder that can cause difficulty remembering recent information, disorientation, and progressive loss of the ability to perform daily tasks and/or take care of oneself.

Alzheimer’s disease can also cause loss of smell in the early stages of the condition. This is believed to happen because of a high concentration of neurofibrillary tangles in the olfactory region of the brain, which are structures formed by abnormal proteins that build up inside neurons.

What to do: treatment should be guided by a neurologist, who may recommend medications to relieve symptoms and slow disease progression, such as donepezil, galantamine, or rivastigmine.

7. Deviated septum

A deviated septum happens when the wall that separates the nostrils is shifted or altered. This can occur due to blows to the nose or local inflammation, causing symptoms such as changes in breathing, loss of smell, headache, and excessive tiredness.

What to do: an ENT specialist may prescribe nasal decongestants and antihistamines to relieve symptoms. In some cases, the doctor may also recommend septoplasty, which is surgery to help correct a deviated septum.

8. Brain tumor

A brain tumor happens when abnormal cells grow in the brain or in the membranes that cover the brain and spinal cord. It can cause loss or reduced sense of smell, severe headache, blurred vision, paralysis, lack of balance, and even seizures.

What to do: treatment varies depending on the size, type, grade, and location of the tumor. The doctor may recommend surgery to remove the tumor, radiation therapy, or chemotherapy, for example.

9. Zinc deficiency

Zinc deficiency can affect organs such as the skin, bones, and nervous system. It may cause loss of smell and taste, diarrhea, photophobia, hair loss, and wounds that take a long time to heal.

What to do: zinc deficiency may be treated with zinc supplements, such as zinc gluconate, zinc sulfate, or other forms of zinc. However, the type and dose of supplement vary depending on each person’s nutritional needs, so zinc should only be used under the guidance of a doctor or registered dietitian.

When to see a doctor

It is advisable to see an ENT specialist or general practitioner when loss of smell is not related to respiratory infections, such as the flu, cold, COVID-19, or sinusitis, or to a deviated septum, for example.

It is also recommended to see a doctor when loss of smell continues even after recovering from a respiratory infection.