If you smell burnt toast but can’t locate the source, you may be experiencing phantosmia. It’s common after an upper respiratory infection, head or nose injury, or bout of allergies.

Smelling smoky or burning smells — including burnt toast — is a common type of phantosmia. Phantosmia is a condition that causes you to smell things that aren’t there. It’s also called olfactory hallucination.

The smells may always be present, come and go, be temporary, or last for a long time. While smelling burnt toast in particular is not diagnostic, smelling something that isn’t there can be a sign of a more serious condition.

Seek emergency medical care

Call 911 or your local emergency services or head to the nearest emergency room if you experience:

Contrary to popular belief, there’s no evidence that suggests phantosmia is a sign of a stroke.

Still, it’s important to be aware of the warning signs so that you can take quick action if one occurs. Fast action improves the odds of recovering fully after a stroke.

Stroke symptoms come on suddenly, without warning. A simple “FAST” test can help you recognize a stroke in yourself or others:

  • F — Face: Smile and look for signs of drooping on one side of the face.
  • A — Arms: Lift your arms and look for a downward drift in one arm.
  • S — Speech: Try to repeat a phrase without slurring. For example, “The early bird catches the worm.”
  • T — Time: Waste no time. Immediately call your local emergency services.

A seizure is an abnormal brain firing. Depending on its location, a seizure could cause phantosmia.

The most common type of seizure that may cause you to smell burnt toast is a temporal lobe seizure, or temporal lobe epilepsy. It can cause a sudden olfactory hallucination that resolves within a few minutes.

Some people experience an aura, or unusual feeling, before the seizure begins. This may involve:

  • déjà vu (when something new feels familiar) or jamais vu (when something familiar feels new)
  • a sick feeling in the pit of your stomach, like you’re falling or riding a rollercoaster
  • a rush of intense fear, panic, anxiety, anger, sadness, or joy
  • an unexpected taste in your mouth
  • hearing unexplained music or sounds

Other symptoms include:

  • blank stare
  • dilated pupils
  • repetitive, uncontrollable movements
  • stiffening or jerking of the body

If you or someone else may be having a seizure, call 911 and go to the nearest emergency room right away.

Issues that begin in the nose, either in the olfactory nerves in the nose itself or in the olfactory bulb just above the nose, account for 52% to 72% of phantom smells.

Nasal polyps

Nasal polyps are soft, painless, noncancerous growths on the inside of your nose.

They’re usually caused by chronic inflammation and are one of the most common causes of issues with your sense of smell. This is because they can damage your olfactory system.

Upper respiratory infection

Even just one infection can damage the olfactory system and cause you to smell things like burnt toast. COVID-19, for example, can disturb the olfactory system and cause long-term phantosmia.

Allergies

Congestion from allergies can temporarily damage your olfactory system and cause you to smell things that aren’t there, like burnt toast. Over-the-counter antihistamines can help alleviate these symptoms.

Head injury

Even minor head injuries can disrupt your sense of smell. This may be due to an injury to the olfactory nerve or to the left frontal lobe.

Mental health conditions

Schizophrenia is typically associated with auditory and visual hallucinations, but olfactory hallucinations are possible. People with severe depression may also experience phantosmia.

Parkinson’s disease

Phantosmia is a common early symptom of idiopathic Parkinson’s disease. It often appears before motor changes and can, therefore, be a potential diagnostic tool.

However, phantosmia is less common in people with genetic Parkinson’s disease.

Migraine episodes

Phantom smells are a rare type of migraine aura. These olfactory hallucinations can happen just before or during a migraine and may last up to an hour.

Alzheimer’s disease

People with dementia may experience any type of hallucination, including phantosmia. These hallucinations usually happen in the later stages of Alzheimer’s disease.

Brain tumor

Your olfactory complex, which is what allows your brain to process smells, is in your frontal and temporal lobes. A tumor in the frontal or temporal lobe can distort your sense of smell and cause you to smell things that aren’t there.

Radiation therapy

Radiation can damage healthy cells near the cancer cells it targets. Because of this, radiation for throat or brain cancer can lead to changes in smell.

These changes are usually temporary and go away within several months after completing treatment.

Neuroblastoma

Neuroblastoma is a rare type of cancer that starts in the nerves that affect your sense of smell. It usually occurs on the roof of your nasal cavity. This can cause issues with nasal nerves, including loss of smell and phantosmia.

Exposure to neurotoxins

Neurotoxins are chemicals that are toxic to your nervous system. Long-term exposure to neurotoxins can alter your sense of smell.

Metals like lead, nickel, and mercury are most likely to cause you to smell odors like burnt toast. Other toxins, such as chemical solvents, may also cause phantosmia, but the link is less clear.

It’s important to make an appointment with a doctor if you experience phantosmia after an injury or alongside other symptoms. This includes:

First, a healthcare professional will take a history of your symptoms. They’ll ask what you smell, when it happens, and how often you smell it. Keeping a log of your symptoms can help make this process easier.

They’ll also take a general medical history and ask about any recent infection or trauma. Next, a doctor will examine your nose, mouth, and throat for inflammation and other signs of infection.

If necessary, they’ll do a nasal endoscopy, which is where they look deep into your nose with a thin tube that has a camera on the end. Then they may test your sense of smell in each nostril.

They may also perform cognitive testing and look for tremors or other changes in motor function. In some cases, a head CT scan or MRI may be necessary.

Burnt toast is a common phantom smell, and it can be a sign of an underlying medical condition. If you smell burnt toast, even if the smell is only temporary or comes and goes, it’s important to consult a healthcare professional.

Treatment will depend on the cause. If it’s caused by an infection, it will likely clear up on its own. In some cases, antibiotics may be necessary.

If the smell is caused by an underlying neurological condition, your healthcare professional will help you find the best treatment options available.