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:

1. Acute sinusitis
2. Chronic sinusitis
3. Common cold
4. Coronavirus disease 2019 (COVID-19)
5. Hay fever
6. Influenza (flu)
7. Nonallergic rhinitis
8. Smoking

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

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

1. Nasal polyps
2. 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:

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