What could cause me to lose my sense of smell?

Marilene B. Wang, MD
Ear, Nose & Throat (Otolaryngology)
A variety of things may cause you to lose your sense of smell. An obstruction or infection within the nose or sinus (such as a cold or sinus infection) will impede your sense of smell. Polyps in the nose block the transmission of smell to the nerves inside the nose. Rarely, there could be a tumor inside the nose that blocks the sense of smell.

A natural loss of the sense of smell due to aging can occur in everybody. Chronic illnesses, such as diabetes, kidney or liver disease, can also lead to losing your sense of smell, as can taking certain medications. 
Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
Losing your sense of smell may be an early warning sign of Parkinson’s disease. The degenerative nerve disorder usually starts slowly and worsens over time, leading with muscle tremors to slowness of voluntary movements, muscle stiffness, imbalance, changes in speech, and dementia.
Catch this debilitating disease early by testing your sense of smell. Start by holding an open rubbing-alcohol swab by your belly button and slowly raising it to your nose. If you can smell the swab 8 to 12 inches away from your nose, your sense of smell is normal. But if you only start to smell it 4 inches away, it indicates a loss of smell.
There are other reasons your sense of smell may be lacking, and alpha-lipoic acid may be able to help in some of those cases. Made naturally in the body and available from food sources like spinach, broccoli, and yeast, alpha lipoic acid has been used for decades in Europe to treat nerve conditions. Try taking just 600 mg daily. It's available in health food stores.
Loss of smell could also be a sign of Alzheimer's.
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Anthony L. Komaroff, MD
Internal Medicine
The nerve endings for your sense of smell start in the upper spaces of the nose. When air passes through your nose, some if it usually flows up around these nerve endings and we smell the scents in the air. If the nerve endings are damaged, then we can lose a part or all of our sense of smell.

One common cause for a total loss of smell is infection. Most often these are viral infections, such as the common cold. Bacterial infections such as scarlet fever can cause the loss as well. If your sense of smell doesn't come back within 6 months of the loss, it is unlikely that it will return.

Anything that blocks the flow of air to the upper part of the nose can also cause a loss of smell. Common causes are nasal allergies and polyps. Often, treating these problems can bring the smell back.

Trauma can cause loss of smell, too. For instance, head injuries or nasal surgery can sometimes cause damage to the nerve endings as they pass through the fine bony openings between the brain and the nose.

Tumors of the nerve itself can also lead to the loss. But this is rare. The loss of smell caused by a tumor usually occurs gradually over many weeks or longer.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.