A stuffy nose from a cold is a common cause for a partial, brief loss of smell. A polyp or swelling inside the nose can lead to a loss of smell. Aging can cause a loss of smell, especially after age 60.

What is smell?

The nose and an area in the upper throat have special cells, called receptors, that discern odors. These receptors send a message to the brain about each smell. The brain then figures out what the smell is.

Any problem along the way can affect the sense of smell. Problems can include a stuffy nose; something that blocks the nose; swelling, called inflammation; nerve damage; or an issue with how the brain works.

Problems with the inner lining of the nose

Conditions that cause congestion or other issues inside the nose may include:

• Acute sinusitis
• Chronic sinusitis
• Common cold
• Coronavirus disease 2019 (COVID-19)
• Hay fever (allergic rhinitis)
• Influenza (flu)
• Nonallergic rhinitis
• Smoking

Blockages in the inside of the nose, called the nasal passages

Conditions that block the flow of air through the nose can include:

• Nasal polyps
• Tumors

Damage to your brain or nerves

The following can cause damage to the nerves to the area of the brain that picks up smells or to the brain itself to:

• Aging
• Alzheimer's disease
• Being around toxic chemicals, such as those used in solvents
• Brain aneurysm
• Brain surgery
• Brain tumor
• Diabetes
• Huntington's disease
• Hypothyroidism (underactive thyroid)
• Kallmann's syndrome (a rare genetic condition)
• Korsakoff's psychosis, a brain condition caused by the lack of vitamin B-1, also called thiamin
• Lewy body dementia
• Medicines, such as some for high blood pressure, some antibiotics and antihistamines, and some nasal sprays
• Multiple sclerosis
• Parkinson's disease
• Poor nutrition, such as too little zinc or vitamin B-12 in the diet
• Pseudotumor cerebri (idiopathic intracranial hypertension)
• Radiation therapy
• Rhinoplasty
• Traumatic brain injury

Losing the sense of smell touches many parts of life. Without a good sense of smell, food might taste bland. It can be hard to tell one food from another.

Losing some of the sense of smell is called hyposmia. Losing all sense of smell is called anosmia. The loss might be brief or long term, depending on the cause.

Losing even some sense of smell can cause a loss of interest in eating. Not eating might lead to weight loss, poor nutrition or even depression.

The sense of smell can warn people of dangers, such as smoke or spoiled food.

Loss of smell caused by colds, allergies or sinus infections usually clears up on its own in a few days or weeks. If this doesn't happen, make a medical appointment to rule out more-serious conditions.

Loss of smell can sometimes be treated, depending on the cause. For instance, an antibiotic can treat a bacterial infection. Also, it might be possible to remove something blocking the inside of the nose. But sometimes, loss of smell can be lifelong.