Occasionally encountering an unpleasant smell is normal. However, several conditions — including those involving the sinuses, nasal passages, and mouth — can cause a bad smell that seems to come from the inside of the nose.

Conditions that may cause a bad smell in the nose include:

  • acute and chronic sinusitis
  • mouth or tooth infections
  • dry mouth
  • some foods, drinks, and medications
  • conditions associated with hallucinations or olfactory damage

Most conditions that cause a bad smell in the nose are not life threatening. However, if the bad smell is severe or chronic, it can negatively impact someone’s quality of life and may require medical attention.

This article discusses the causes of a bad smell in the nose, as well as treatments and prevention methods. Several conditions are commonly associated with a bad smell inside the nose, and we cover many of them below.

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A person may experience a bad smell in their nose if they have acute or chronic sinusitis.

Sinus infection, called sinusitis, affects around 31 million people in the United States.

Sinusitis causes symptoms such as sinus inflammation and nasal congestion, which can interfere with a person’s sense of smell.

The condition can also cause bad breath and a discolored, bad-smelling discharge in the nose and back of the throat, all of which may create a bad smell in the nose.

Acute sinusitis typically lasts for around 3–8 weeks, while chronic cases can last for longer than 8 weeks. A species of bacteria usually causes sinusitis, though viruses, fungi, and molds can also cause it.

Cavities, or holes in the teeth, can trap bacteria that release unpleasant gases such as sulfur when they break down. Cavities usually arise due to tooth decay or gingivitis, which can include inflamed gums or gum disease.

These unpleasant gases, which become foul-smelling odors, can travel through small holes in the back of the mouth that connect to the sinuses and cause a bad smell in the nose.

Poor oral hygiene increases the number of food particles left in the mouth that can decay, increasing the risk of developing a bad taste or smell in the mouth.

Dental issues can also increase the risk of developing plaque, which is a thick film of bacteria that can cause tooth decay and inflame the tissues between the teeth and gums (a condition called periodontitis).

Foods and drinks are full of microscopic molecules that stimulate the sense of smell.

Most of our ability to enjoy the taste and smell of food and drink relies on molecules traveling to the sinuses through a passageway near where the roof of the mouth connects to the nose.

All foods release smells as our bodies break them down and digest them. However, certain foods and drinks, as well as some drugs, may linger in the mouth or trigger an unpleasant smell in the nose, especially:

  • garlic and onions
  • coffee
  • spicy foods
  • nitrates and nitrites
  • amphetamines
  • phenothiazines

Dry mouth, or xerostomia, can develop when the flow of saliva is not adequate. Most people with dry mouth feel continuously parched and have swollen nasal passages.

Saliva constantly removes unwanted microbes and particles from the mouth. It also neutralizes acids.

So, when there is not enough saliva, a person is more likely to experience conditions that can cause a bad smell or taste in the mouth and nose, such as bad breath and tooth decay.

Dry mouth is also a common side effect of several medications. Causes of dry mouth include:

  • breathing through the mouth
  • dehydration
  • pain medications
  • decongestants
  • antihistamines
  • diuretics
  • salivary gland conditions, such as Sjogren’s syndrome

Tobacco products contain chemicals that stain and weaken the teeth and gums, thus increasing the risk of tooth and gum disease. Tobacco can also give the breath an unpleasant odor.

Smoking can also reduce someone’s ability to taste and smell food properly, which may cause someone to smell odors that they perceive as foul, but which may not actually be bad.

People with phantosmia smell things that are not there. It occurs when a condition interferes with a person’s sense of smell.

Everyone with phantosmia smells a slightly different scent, but most people experience something that smells:

  • burnt
  • metallic
  • similar to chemicals
  • rotten
  • decayed
  • similar to feces

Phantosmia only affects around 10–20% of people with smell disorders. However, a wide range of conditions may cause phantosmia, including:

Learn more about phantosmia here.

Some digestive conditions, such as acid reflux, can cause bad breath and a bad taste in the mouth.

Also, although fairly benign conditions are usually behind a bad or unusual smell in the nose, it is rarely linked to more systemic or serious health conditions, which may include:

  • diabetes, which may cause a sweet smell
  • liver disease, which may cause a strong musty smell
  • kidney disease, which may cause an ammonia-like smell

The best way to treat a bad smell in the nose depends on the underlying condition.

That said, there are some home remedies that can help reduce a bad smell in the nose:

Try a homemade saltwater rinse

Using a saltwater rinse can help temporarily reduce the intensity of a bad smell in the nose.

To make a saltwater rinse at home:

  1. Boil 460 milliliters of water, then leave to cool.
  2. Mix 1 teaspoon (tsp) of salt and 1 tsp of baking soda into the water while it is still quite warm.
  3. Wash the hands well with soap and water.
  4. Standing over a sink or bowl, pour some of the mixture into the cupped palm of one hand.
  5. Lean over the sink and sniff some of the mixture into one nostril at a time, then let it run out of the nose. It may help to keep the other nostril closed with a finger while sniffing.
  6. Repeat steps 4 and 5 a few times.
  7. Dispose of any unused solution.

People can also use a soft rubber ear bulb syringe or a commercial nasal saline rinse product from a drug store.

Stay hydrated

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Dehydration may cause conditions that result in a bad smell in the nose.

Many conditions that result in a bad smell in the nose have dehydration as their root cause. How much liquid someone needs each day depends on their age, activity levels, and diet, among other factors.

People whose bodies do not make enough saliva can use artificial saliva or try sugar-free candies or gums to encourage saliva production.

Foods that require a lot of chewing, such as fiber-rich fruits and vegetables, can also promote saliva production.

Practice good dental hygiene

Having good oral hygiene can help treat several conditions that cause a bad smell in the mouth and nose. Some recommendations from the American Dental Association include:

  • Brush the teeth with a fluoride-based toothpaste for 2 minutes twice daily.
  • Floss daily.
  • Clean the tongue daily with a toothbrush or a tongue scraper.
  • Clean dentures and other dental gear daily.
  • Chew sugarless gum for 5 minutes after meals.
  • Cut back on foods and drinks that contribute to dehydration, such as coffee and alcohol.
  • Quit smoking and tobacco use.
  • Have dental checkups and cleanings frequently.

Use over-the-counter medications

Some over-the-counter (OTC) medications may also help treat conditions that can cause a bad smell in the nose. OTC medications include:

  • Nasal decongestant spray: This can help shrink inflamed nasal passageways and increase sinus drainage. Most nasal decongestant sprays are useful for 3–4 days.
  • Antihistamines: These block inflammation, which can help open swollen nasal and sinuses pathways.

Some conditions that cause a bad smell in the nose require medical attention. Sinus or nasal infections that last longer than 7–10 days, for example, generally require antibiotic treatment for 3–28 days.

A doctor or allergist may also prescribe certain medications or therapies to help a person manage conditions that cause a bad smell in the nose, including:

  • Topical nasal corticosteroids sprays: These help reduce nasal and sinus inflammation.
  • Surgery: This can reverse structural problems such as nasal bone defects, nasal polyps, or closed airways.

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Certain lifestyle changes, such as practicing good dental hygiene, may help reduce the risk of developing a bad smell in the nose.

Depending on the condition that causes it, making certain lifestyle changes can help reduce the risk of developing a bad smell in the nose. Lifestyle changes include:

  • practicing good dental hygiene
  • staying hydrated
  • eating fiber-rich foods
  • avoiding foods and drinks that cause dehydration, such as caffeine and alcohol
  • using antihistamines or decongestants to treat nasal or sinus inflammation
  • avoiding foods and drinks that cause bad smells in the mouth, such as garlic and onions
  • not smoking or using tobacco products
  • talking to a doctor about reducing or switching medications that may be linked to dry mouth
  • having regular dental checkups and treating dental or mouth infections

Sinusitis, mouth infections, and certain foods, drinks, and lifestyle habits are usually behind bad smells in the nose.

People can usually get rid of bad smells in the nose by using home remedies, trying OTC medications, and making lifestyle changes.

However, a bad smell in the nose can decrease someone’s quality of life and cause complications such as malnutrition. It can also be a sign of underlying conditions that require medical treatment.

A person can talk with their doctor about severe or chronic bad smells in the nose, those that do not respond to home remedies, or those that last longer than a week.