What Causes Scent Sensitivity?

Dr. O. Mutlu Topal · Medical Doctor · Last updated: October 5, 2026

Written by Dr. O. Mutlu Topal, Medical Doctor (Ankara University Faculty of Medicine)

A complaint I hear often goes like this: “The smell of the onions my neighbor is frying comes up from three floors down; nobody at home notices it, and I feel like I am going to throw up.” The person who says this sometimes learns two weeks later that she is pregnant. And sometimes the person has migraine, and the culprit is not the onion but the perfume of someone who sat down next to them on the bus.

That is how scent sensitivity is: it comes in through doors that are very different from one another. In medical language it is often called hyperosmia, but the name is not quite right: the nose is not picking up more sharply, the brain is reacting more harshly. That is why smell tests mostly come back normal. Sensitivity is not considered a disease in itself; it is a sign. The real job is to find out what it is a sign of.

What exactly is scent sensitivity?

If the same scent was ordinary yesterday and today it turns your stomach, gives you a headache or makes you leave the room, what has changed is not the scent itself or your nose; it is the strength of the reaction that the center processing the scent gives to it. So we do not look for something in the nose; we look at what changed in your body in that period: a new medication, a late period, a week without sleep, an unsettled stomach.

What are the most common causes?

Do not diagnose yourself by looking at the table; from what I see in practice, the great majority of these complaints come down to one of the first four rows, but which one it is, the examination decides.

When does scent sensitivity start and end in pregnancy?

You can think of the hormones that rise in the first weeks of pregnancy (above all hCG, that is, human chorionic gonadotropin, and estrogen) as putting the smell center into alarm mode. For many women, scent sensitivity is the first sign, noticed even before the pregnancy test. Its calendar is mostly the same as that of nausea: it starts in weeks four to six, enters its most intense period around week nine, and recedes by weeks sixteen to twenty in most women. In one or two of every ten women it lasts longer; this too is within normal.

• Weeks 4–6: It starts, most often together with nausea
• Around week 9: The most intense period
• Weeks 16–20: It recedes in most women

Escaping scents is not possible in this period anyway; but airing the kitchen, using the oven and boiling in place of frying, putting perfume and strongly scented cleaning products away on the shelf for a while, and eating meals lukewarm or cold (hot food gives off more smell) lighten the load noticeably. There is also lemon: a small randomized trial showing that the scent of lemon eased pregnancy nausea has been published (Yavari Kia et al., 2014). It is not a miracle; it draws attention to another scent.

Migraine and scent: which one triggers which?

Although it varies from study to study, roughly half of people with migraine say that scents start an attack (Kelman, 2007). Intolerance to scents during an attack has a name of its own: osmophobia. Because it is not much seen in tension-type headache, some neurologists use it as a clue in diagnosis (Zanchin et al., 2007). Pay attention to the order: first comes the scent, then within half an hour to a few hours the pain. In some patients the attack has already started, and scent sensitivity is a part of the pain.

The scents blamed most often are perfume, cigarette smoke, gasoline and exhaust, paint and paint thinner, frying, and some cleaning products. The only way to find your own trigger is to keep a record: when the pain starts, note what you smelled in the last two hours. After three or four attacks the pattern shows itself.

Why do scent sensitivity and nausea come together?

Scent and nausea are in the same region of the brain. The region that processes scent information is directly connected to the vomiting center; this connection is an evolutionary protection, the mechanism that makes us stop before eating spoiled food. In pregnancy, in migraine or in stomach disease this line runs oversensitive, and even an innocuous scent triggers nausea.

In people with reflux or gastritis there is one more, separate mechanism: when the stomach is already upset, the smell of food prepares the stomach to secrete, and the discomfort increases. In these people, once treatment for the stomach starts, the scent complaint mostly recedes as well.

Scent sensitivity in children

Some children overreact to certain scents (food, soap, the school cafeteria). Most of the time this is a matter of sensory sensitivity and decreases as the child grows. If, along with scent, there is also an overreaction to sound, to touch or to clothing labels, and it disrupts daily life, the pediatrician may ask for a developmental evaluation. If there is headache, abdominal pain or not wanting to go to school along with the reaction to scent, this needs to be said too; migraine in children looks different from migraine in adults and often comes with abdominal pain.

When should you see a doctor, and which department?

If any of the following is present, do not wait:

• A severe, newly started headache together with scent sensitivity
• Constant vomiting, weight loss, not being able to eat
• Constantly smelling an odor that has no source around you (burning, rotten)
• A sudden decrease in the sense of smell
• Symptoms that suggest a seizure along with the scent, such as staring off for a few seconds, a blank spell, or lip smacking
• Accompanying symptoms such as a vision disturbance, loss of balance, or numbness
• Sensitivity that lasts longer than three months and whose cause cannot be found

The choice of department depends on the cause. If you are pregnant, obstetrics and gynecology; if headache is in the foreground, neurology; if nausea and reflux are in the foreground, internal medicine or gastroenterology; if there is nasal congestion, discharge or a disturbance in the sense of smell, ear, nose and throat. If you are not sure, start with your family physician, who will refer you to the right department.

What should you prepare before going to the doctor?

Scent sensitivity is not something that can be shown in an examination; you have to describe it and tell it. The important notes are these: when it started (in weeks), which scents (perfume, food, cleaning product; one particular scent or all of them), the accompanying symptoms (nausea, headache, vomiting, weight change, menstrual pattern), and the medications started or changed in dose in the last three months. Keeping a short one-week diary on your phone and bringing it along matters for giving the physician information. If there is a chance of pregnancy, say so in your first sentence; it changes both the choice of tests and the choice of medication.

What can you do at home?

1. Air the rooms often.
2. Give up strongly scented products (perfume, room spray, heavy detergent) for a while.
3. Use the oven in place of frying.
4. Wear a mask outdoors; in crowds and in traffic it lets some people breathe more easily.

A regular sleep schedule and regular meals help reduce sensitivity that comes from migraine and anxiety. Patience is part of the list too: most of the causes other than pregnancy and migraine resolve on their own once the underlying problem is solved.

Which medications can cause scent sensitivity?

The list of medications that change the sense of smell is long. Those reported to sharpen scents or make them bothersome: some antidepressants, birth control pills and hormone treatments, a change in thyroid hormone dose. Those that distort scents (the smell of food seeming rotten): some antibiotics, chemotherapy drugs, nasal decongestant sprays used for a long time. A distorted sense of smell is also described by the patient as “sensitivity” most of the time. The common point is this: the complaint appears in the weeks after starting the medication or after the dose changes. If you notice such timing, do not stop the medication on your own; tell the physician who wrote the prescription, “after this medication, scents started to bother me.” In many cases a dose adjustment or another equivalent medication is enough; with medications that cannot be changed, the complaint mostly recedes when the treatment ends.

Scent sensitivity at work and at school

The hardest place is not home; it is the settings you cannot control. In an open office, the perfume at the next desk; the room fragrance in the shuttle bus; the frying smell of the school cafeteria. Explaining the situation in one sentence works: saying “I have a sensitivity to scents, and it triggers my migraine” or “I am pregnant, and scents make me nauseous” is accepted far more easily than saying “your perfume bothers me.” There is also the matter of position; a desk near the window, the front seat in the shuttle bus, a corner near the ventilation in the cafeteria is enough most of the time. There is also a small thing to carry with you: a slice of lemon, or just cold water; it does not remove the scent, but it draws the attention and interrupts the nausea. For children, write a short note to the teacher; in the cafeteria or in art class (the smell of paint), the child is then allowed to leave the classroom when feeling unwell.

Sources

• Kelman L. The triggers or precipitants of the acute migraine attack. Cephalalgia. 2007;27(5):394–402. doi:10.1111/j.1468-2982.2007.01303.x
• Zanchin G, Dainese F, Trucco M, Mainardi F, Mampreso E, Maggioni F. Osmophobia in migraine and tension-type headache and its clinical features in patients with migraine. Cephalalgia. 2007;27(9):1061–1068. doi:10.1111/j.1468-2982.2007.01421.x
• Yavari Kia P, Safajou F, Shahnazi M, Nazemiyeh H. The effect of lemon inhalation aromatherapy on nausea and vomiting of pregnancy: a double-blinded, randomized, controlled clinical trial. Iran Red Crescent Med J. 2014;16(3):e14360. PMC4005434

Frequently Asked Questions

Is scent sensitivity a sign of pregnancy?

It can be. In many women it is one of the first signs, but on its own it does not mean pregnancy; a test needs to be done.

Can scent sensitivity occur before a period?

Yes. In some women the premenstrual hormone fluctuation sharpens the reaction to scents, and it passes with the period.

Which disease is scent sensitivity a symptom of?

Not of one single disease. Pregnancy, migraine, stomach conditions, anxiety and some medications are its most common causes.

How does scent sensitivity go away?

In most patients it recedes once the cause is found and corrected. In pregnancy it mostly fades on its own in weeks sixteen to twenty; in migraine it decreases with attack treatment.

Which doctor do you see for scent sensitivity?

Neurology if headache is in the foreground, internal medicine if nausea is in the foreground, ear, nose and throat if there is a nasal complaint, obstetrics and gynecology in pregnancy. If you are undecided, the family physician.

Does scent sensitivity become permanent over time?

Rarely. In most people it is periodic and disappears once the underlying cause passes.