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Olfactory Nerve: What to Know

Medically Reviewed by Poonam Sachdev on October 07, 2022

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What Is the Olfactory Nerve?

Your first and shortest cranial nerve is the olfactory nerve. This nerve is one of two that don’t connect with your brainstem. Your olfactory nerve anatomy is a part of your central nervous system. 

There are about six million to 10 million olfactory sensory neurons in each nostril. That means there’s a lot of work happening inside of your nostrils to help you smell what’s around you or the food you’re eating. 

Olfactory nerve location. These nerves are in a portion of each nasal cavity. Your olfactory nerve gets its blood supply from your cerebral or olfactory artery. All this action takes place in the nasal cavity, though the olfactory nerve comes from your brain. There are 20 or more branches of your olfactory nerve in the roof of your nasal cavity.

How Does the Olfactory Nerve Function? 

The primary olfactory nerve function is to help you smell and taste foods. 

Your olfactory nerve stems from your olfactory epithelium, which comes from your nasal pits. From birth, your olfactory nerve's origin goes on to your nose and primary palate. The nerves and cells combine to help you smell.

A lot of the work is done when your olfactory neurons send messages to your brain in the olfactory bulb. These messages send information to other parts of your brain and help you combine taste and smell.

The olfactory sensory neurons connect your senses of smell and taste. When you chew food, a smell is released and picked up by these neurons through the second channel in your throat. When that channel gets blocked from a stuffy nose, you lose your ability to taste and smell.   

Signs Something Could Be Wrong With Your Olfactory Nerve

Losing your sense of smell can be more dangerous than you might think. A scent can help alert us to problems around us. If there's a fire, a moldy piece of food, or something else, our noses can sometimes alert us before our eyes and ears do.

Sometimes you might not lose a total sense of taste and smell. Sometimes, you may only lose the ability to taste certain flavors, such as sweet things or bitter things. The same applies to smell. When your sense of smell starts to change, something you once enjoyed the scent of could become repulsive.  

Certain conditions, like olfactory neuroblastoma, can cause olfactory nerve damage, resulting in multiple symptoms. These include: 

  • A stuffy or blocked nose
  • Worsening congestion
  • Pain around your eyes
  • Watery eyes
  • Nosebleeds

In more severe cases, if there's a problem with your olfactory nerve, you may notice face or tooth numbness and loose teeth. Along with a worsening sense of smell, you may have a change in vision, ear pain, loose teeth, or trouble opening your mouth.

What Conditions Affect the Olfactory Nerve?

Quite a few conditions affect the olfactory nerve. Most of these conditions also have major effects on your brain and your sense of taste.  

Olfactory neuroblastoma is cancer that occurs on the roof of your nasal cavity. This rare form of cancer forms on the bone between your eyes and your skull. Loss of smell can be the first indicator of this cancer. That's why it's important to talk to your doctor if you have the symptoms listed above. 

Parkinson's disease and Alzheimer's disease are conditions that affect your nervous system, including the olfactory nerve. Early signs of problems with your olfactory nerve can indicate Parkinson's or Alzheimer's. 

Anosmia and hyposmia are two conditions that affect your olfactory nerve. Anosmia is a complete lack of smell. In rare cases, a child can be born without a sense of smell, although this condition typically occurs later in life. Hyposmia is a heightened sense of smell that can sometimes be overwhelming and revolting. 

Parosmia is a smell disorder that changes how you smell things. For example, if you once liked the smell of something, you might now be nauseated by it. Phantosmia is a smell disorder in which you smell things that aren't there. 

Other conditions that affect your olfactory nerve include: 

  • Multiple sclerosis
  • Obesity
  • Diabetes
  • Hypertension
  • Malnutrition

Problems with nerves in your brain can be severe. It's best to talk to your doctor as soon as possible if you notice problems with your senses. You should act fast, whether it's taste, smell, touch, sight, or hearing.

How to Protect Your Olfactory Nerve

While you can't always prevent certain conditions like cancer or Parkinson's, there are steps you can take to protect your olfactory nerve. 

Your olfactory nerve has a vital role in your nervous system. If that nerve becomes damaged, it creates a lot of consequences for other parts of your head and nose. Keeping your olfactory nerve protected is essential. Fortunately, your olfactory neurons can regenerate after an injury, so a loss of smell is most likely temporary.

Protecting your head, neck, and brain by wearing proper helmets and protection during certain activities can help you prevent a brain injury. To reduce the likelihood and severity of COVID-19, which has caused a loss of taste and smell in some people, stay up to date on the vaccine and boosters. 

Your nose has many neurons, making them sensitive to gases and fumes. Ensure you're wearing proper protection from chemical exposure. You should also limit smoking or vaping.

Smell training is also an option if you've developed a smell disorder. A recent study indicated that using a kit over a few months can help your smell pathways recover and boost neuron regeneration. 

Talk to your doctor if you've had an abrupt loss of smell or taste. They'll be able to help you diagnose the cause and start on a treatment plan. 

Show Sources

SOURCES:
Boys Town National Research Hospital: “Taste and Smell Disorders.”
BrainFacts.org: “Making Sense of Scents: Smell and the Brain.”
Cleveland Clinic: “Olfactory Nerve.”
Deutsches Arzteblatt International: “Olfactory Dysfunction: Common in Later Life and Early Warning of Neurodegenerative Disease.”
Harvard Health Publishing: “Smell disorders: When your sense of smell goes astray.”
Helwany, M., & Bordoni, B., StatPearls, “Neuroanatomy, Cranial Nerve 1 (Olfactory),” StatPearls Publishing, 2021.
JAMA: “What Is Anosmia?”
Johns Hopkins Medicine: “Olfactory Neuroblastoma.”
NIH: “Smell Disorders.”
Radiopaedia: “Olfactory nerve.”

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