Overview of Hyperosmia

A strong sense of smell has pros and cons

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Hyperosmia is a heightened sensitivity to smell. It can occur acutely (suddenly) due to conditions like migraine, or chronically (long-term) as a result of certain autoimmune and neurological conditions like epilepsy. Hyperosmia can also be hereditary, but in some cases, it occurs without any clear cause.

Hyperosmia is often unpleasant, especially when it results in nausea. While it usually isn’t necessary to seek treatment for hyperosmia, you may find that some coping strategies, like wearing a mask, are helpful for easing the negative effects of this sensory condition.

This article discusses the causes and symptoms of hyperosmia. It covers how hyperosmia is diagnosed and provides a variety of treatments and coping strategies for dealing with a heightened sensitivity to smell.

Pregnant woman smelling orange with her eyes closed

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Hyperosmia Symptoms

With hyperosmia, strong or unpleasant odors can be overwhelming to the point of nausea and even vomiting. Interestingly, your sense of smell may be intensified for some odors but less so for others.

  • Mood shifts: When odors are pleasant, they can have a positive effect on your mood. These rewarding smells may be able to improve your mood or reduce anger. Yet, the opposite is true for unpleasant odors. Less-than-pleasant smells can impair your working memory and evoke negative emotions.
  • Trigger smells: People with hyperosmia can have "trigger smells," or smells that are particularly offensive to them. Trigger smells can make you feel nauseated or disgusted. Sometimes, the offending smell can be so disagreeable that it triggers a migraine.

There is a strong relationship between hyperosmia and osmophobia (aversion to certain smells). Each of these conditions can lead to the other.

  • Fear of smells: Despite the name, osmophobia is not necessarily a fear of bad smells, but rather an extreme aversion or disgust for them. In some cases, osmophobia can progress to fear of a certain smell if you experience anxiety over the negative effect that the smell could have on you.

Hyperosmia has its benefits, too. Some people who were born with hyperosmia are described as “super smellers” and are able to detect and identify subtle aromas with great precision.

This heightened ability may allow super smellers to pick up on some medical conditions by scent alone. This phenomenon was demonstrated in a 2019 study published by the American Chemical Society, in which a super smeller accurately detected the distinctly "musky" smell of Parkinson's disease (PD) out of 64 sebum samples collected from the upper backs of people with and without PD.

Some practical advantages of hyperosmia include detecting the location of a dangerous smell, like smoke or a chemical leak, or noticing that food is rotting.

Causes of Hyperosmia

Some people naturally have a heightened sensitivity to smell all the time. This is believed to be genetic, and it has been linked with the SCN9A gene, which codes for sodium channels (a component of nerve cells) in the body. This may not be the only gene associated with hyperosmia, however, and the condition could be related to several genes.

You may also have episodes of hyperosmia at certain times, such as during pregnancy. Some medical conditions can make you develop lasting hyperosmia, either suddenly or gradually.

Common Causes

Several conditions are often characterized by hyperosmia and osmophobia. These conditions are typically episodic, like epilepsy and migraine. Other conditions, such as toxin exposure, are not common and may be difficult to pinpoint.

Pregnancy: An increased sensitivity to smells is commonly reported in the first and second trimesters of pregnancy. Hyperosmia can trigger nausea and vomiting, and it has been associated with hyperemesis gravidarum (excessive vomiting during pregnancy typically requiring medical treatment and intravenous or IV fluids).

The exact physiology for the heightened sense of smell in pregnancy isn't known but there are theories. One is that increased levels of the hormone human chorionic gonadotropin (hCG) may play a role. Another is that people may be more aware of odors during pregnancy and react more strongly to them, rather than truly sensing them more acutely.

Migraines: Heightened sensitivity, as well as repulsion by certain odors, is very common in the pre-migraine premonitory stage, as well as during the peak of a migraine. Hyperosmia tends to diminish after a migraine subsides, but people with recurrent migraines tend to have increased sensitivity to smells even during migraine-free times.

Upper respiratory infection: A sinus infection can give you a stuffy nose. While your smell detection can be obscured, you can develop hyperosmia to some smells, too.

Epilepsy: An exaggerated sense of smell can occur as a pre-seizure aura. In rare instances, hyperosmia can also be present during or after a seizure.

If you have epilepsy-associated hyperosmia, you might smell things that others don’t smell at all—either because the odor is subtle or because it may not be present at all.

If the odor is not present at all, you may actually be experiencing what's known as phantosmia (phantom smells), although your symptoms may be described as hyperosmia.

Toxin exposure: There are numerous reports of hyperosmia beginning after exposure to toxins such as zinc or manganese. Hyperosmia may be just one of many consequences of chemical toxicity. Sometimes, this effect becomes obvious after several people who were exposed to the same chemical are diagnosed with similar effects.

Neurological and Immune Conditions

Hyperosmia has been reported in association with a number of conditions, including:

An alteration in smell sensation is not the predominant or most common symptom of any of these conditions, but hyperosmia has been reported frequently enough that it is among the well-recognized effects.

Rare Causes

Neurological conditions, particularly Alzheimer’s disease, Parkinson’s disease, and stroke, are frequently associated with hyposmia, which is a decreased sensitivity to smell.

While hyposmia is usually the cause of decreased appetite and weight loss, hyperosmia often accompanies hyposmia. This is because there is an alteration of the whole olfactory (smelling) system, not just a decrease in function.

Furthermore, it is usually the unpleasant smells that are most noticeable, although this could be simply because people are more likely to notice and react to unpleasant smells than to pleasant smells.

Physiological Causes

Odor detection and identification are controlled by the olfactory nerve, also described as cranial nerve one or the first cranial nerve. Smell receptors on the surface of the nasal passages activate the olfactory nerve, which sends messages to the brain’s cerebral cortex, allowing you to recognize and react to those odors.

Dysfunction of your sense of smell can occur due to problems with the receptors, the nerve, or the areas of the cerebral cortex (hippocampus, orbitofrontal cortex, and insula) that integrate those messages.

Each cause of hyperosmia is due to a deficit somewhere along this pathway. For example, hyperosmia in epilepsy is caused by altered activity in the cerebral cortex, while hyperosmia associated with an upper respiratory infection is caused by a problem with superficial odor detection in the nasal passages.

Super-smellers have been found to have an enlarged hippocampus, which is an area of the brain typically associated with emotions and memory, and orbitofrontal cortex, where odors are consciously recognized.

Hormones may also play a role in smell sensitivity. One smell study found that people taking oral contraceptives, which affect the naturally cycling hormones, were not as sensitive to smell as people who were naturally menstruating.

Psychological Causes

Psychological factors can affect how you perceive sense of smell. While anxiety does not necessarily cause hyperosmia, there seems to be a connection between these two conditions. One study found that people who were disturbed by their heightened sensitivity to smell tended to have higher levels of anxiety, life stress, and depression compared to those who were not bothered by a heightened smell sensitivity.

Having anxiety and an odor sensitivity impairment may heighten your ability to detect a potentially dangerous situation. People sensitive to anxiety and odors weren't better able to detect a harmless rose-like odor in the study than people with a heightened sense of smell but without the anxiety factor. However, they were better able to detect a dangerous smoke-like smell.

How Is Hyperosmia Diagnosed?

Hyperosmia is typically diagnosed based on your symptoms. It is not usually the only symptom of any medical condition. However, when you experience the symptoms of hyperosmia, it can be a clue that the underlying cause is acting up.

For example, if you are frequently repulsed by food before your migraines, this can be an indication that you should take your medication. If you are trying to get pregnant, you may feel disgusted by the odor of the cafeteria at work even before you have a positive pregnancy test.

Try to observe this symptom without necessarily diagnosing yourself. Pending an official test, you won’t know exactly what is causing your heightened sense of smell.

Diagnostic Testing

Your healthcare provider may administer a diagnostic test to verify that you have hyperosmia. The University of Pennsylvania Smell Identification Test (UPSIT) is a 40-item test used to diagnose smell defects caused by diseases such as Alzheimer’s disease and Parkinson’s disease.

Your score on this test can be compared to the average to assess whether you have hyperosmia.

Differential Diagnosis

There are a few conditions that can seem like hyperosmia. You may benefit from treatment if you are experiencing these similar conditions.

Olfactory reference syndrome (ORS) is a rare condition in which people are paranoid about their own body smell. It is characterized by unusual and unwarranted apprehension about your own body odor.

This could stem from a life situation, such as experiencing or witnessing embarrassment or humiliation about body odor. It could also be due to true body odor that is too mild for others to detect, but that you can pick up on because of your own heightened sensitivity to smell.

Another similar condition, parosmia, is an altered perception of smell, in which some odors are consistently detected incorrectly. This disorder is associated with a reduced volume of the hippocampus and other areas of the brain that control the sense of smell.

There are all types of sensory hallucinations, which are altered perceptions or perceptions of things that are not there. An olfactory hallucination is a fixed belief that you smell some type of odor that doesn’t exist.

Hallucinations are a sign of psychosis, which is a very serious disorder that requires treatment with prescription antipsychotics. Psychosis can occur due to a disease of the brain, or it can be a medication side effect.

Treatment for Hyperosmia

Hyperosmia is treatable, to a degree. But you may not want medication for your hyperosmia.

If you have migraines or if you are pregnant, your other symptoms may be more concerning for you. If you have lupus, MS, or vitamin B12 deficiency, treatment of your underlying condition is the best way to minimize your hyperosmia.

However, if hyperosmia is interfering with your quality of life, there are a few medical approaches you can take to alleviate this problem.

Antiemetics

Over-the-counter (OTC) and prescription medication can help control nausea and vomiting if this is the most distressing aspect of your hyperosmia. Most of the time, OTC medications like Dramamine (dimenhydrinate), Antivert (meclizine), and Benadryl (diphenhydramine) are enough to control nausea and vomiting.

Check with your healthcare provider or pharmacist before using antiemetics because they might not be safe for you if you are pregnant or taking other medications. The most common prescription-strength antiemetics include Compazine (prochlorperazine), Reglan (metoclopramide), and Zofran (ondansetron).

Nerve Ablation

In rare situations, hyperosmia can be such a severe problem that you may need surgery. This will decrease the function of the olfactory nerve so that the odors you smell will not prevent you from eating or cause you to eat so much that your health is at risk.

This option should be discussed with your healthcare provider in order to determine if it’s the best treatment method for you.

Coping With Hyperosmia

If you have hyperosmia, there are a number of practical steps you can take to manage your condition. You may need to wear a mask if you work in a setting with strong odors. You can also try to disguise offending smells by chewing gum or sucking on candy or a mint.

Some people can’t stand to be around certain odors at all and might not be able to work in a hospital or a factory that contains distress-inducing odors. If that is your situation, you may need to make a change to your work or home environment to eliminate your exposure to triggering odors.

Summary

Hyperosmia is rarely a major problem by itself, but it can be a sign of one. If you notice hyperosmia as a recurring symptom that precedes an impending health problem, such as an MS exacerbation, a migraine, an allergy attack, or a seizure, you may be able to take medication in time to minimize the effects of an attack.

If your hyperosmia is interfering with your life, talk to your healthcare provider and get treated so that aromas won’t limit your ability to socialize, eat, work, or enjoy life.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
Heidi Moawad, MD

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.