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Aspiration Pneumonia and Chemical Pneumonitis


Sanjay Sethi

, MD, University at Buffalo, Jacobs School of Medicine and Biomedical Sciences

Reviewed/Revised Feb 2024

Aspiration pneumonia is lung infection caused by inhaling mouth secretions, stomach contents, or both. Chemical pneumonitis is lung irritation caused by inhalation of substances irritating or toxic to the lungs.

  • Symptoms include cough and shortness of breath.

  • Doctors make the diagnosis on the basis of the person’s symptoms and a chest x-ray.

  • Treatment and prognosis differ depending on the substance that was aspirated.

Aspiration pneumonia and chemical pneumonitis are often considered together because they both involve lung inflammation caused by inhaling substances that irritate the lungs. The inflammation makes the lungs more susceptible to bacterial infection. Drowning Drowning Drowning occurs when submersion in liquid causes suffocation or interferes with breathing. During drowning, the body is deprived of oxygen, which can damage organs, particularly the brain. Doctors... read more may also cause inflammation of the lungs and is discussed elsewhere.

Aspiration Pneumonia

Tiny particles from the mouth frequently dribble or are inhaled (aspirated) into the airways. Usually they are cleared out by normal defense mechanisms (such as coughing) before they can get into the lungs and cause inflammation or infection. When such particles are not cleared (because of impaired defense mechanisms and/or because the volume of aspirated material is large), aspiration pneumonia can develop.

Material aspirated from the mouth and throat is more likely to contain bacteria, which can cause bacterial pneumonia. Material aspirated from the stomach is usually very acidic and can severely damage the lungs even before infection develops.

People who are especially at risk of aspiration pneumonia include people who

Symptoms of aspiration pneumonia do not begin for at least a day or two. The most common symptom is

  • Cough

The cough produces sputum (thick or discolored mucus). The sputum sometimes smells foul.

Other symptoms of aspiration pneumonia include

  • Fever

  • Shortness of breath (dyspnea)

  • Chest discomfort

Doctors usually make the diagnosis of aspiration pneumonia based on finding signs or symptoms in people who have any of the risk factors described above.

A chest x-ray confirms the diagnosis of pneumonia. If the x-ray shows an abnormality in certain portions of the lungs, such as the bottom of the lungs (a common location for aspirated material), aspiration is more likely to be the cause.

For people who have conditions that increase their risk of aspiration, doctors may stop or reduce the dosage of medications that cause sedation. Raising the head of the bed slightly can help prevent food, liquid, or acid in the stomach from moving up into the throat and then down into the lungs. Consuming specific food textures or thickened liquids also helps reduce the risk of aspiration. A speech pathologist may teach the person specific swallowing techniques (for example, swallowing while tucking the chin toward the chest) to further reduce the risk of aspiration.

Chemical Pneumonitis

Chemical pneumonitis occurs when a person inhales (aspirates) material that is toxic to the lungs. The problem is more the result of irritation than infection. A commonly inhaled toxic material is stomach acid, so that chemical pneumonitis may result whenever a person inhales what has been vomited up. Inhalation of vomit can occur when a person who vomits is not completely awake, as can happen after a seizure or a drug or alcohol overdose or when a person awakens from anesthesia.

Chemical pneumonitis may also be caused by inhalation of laxative oils (such as mineral, castor, and paraffin oils) and hydrocarbons (such as gasoline, kerosene, and petroleum products).

Symptoms of chemical pneumonitis include sudden shortness of breath and a cough that develops within minutes or hours. Other symptoms may include fever and pink frothy sputum. In less severe cases, the symptoms of aspiration pneumonia may occur a day or two after inhalation of the toxin.

The diagnosis of chemical pneumonitis is usually obvious to doctors from the sequence of events if this information is available. Chest x-rays and measuring the concentration of oxygen in a blood sample may help.

Although antibiotics are not usually effective for this condition, they are often given because doctors cannot easily distinguish chemical pneumonitis from a bacterial aspiration pneumonia, and often a bacterial pneumonia can develop as a complication of chemical pneumonitis.

Doctors may recommend various strategies to help prevent chemical pneumonitis in people at risk. These include stopping or reducing the dosage of medications that cause sedation. They may also suggest that the head of the bed be raised slightly to prevent food, liquid, or acid in the stomach from moving up into the throat and then down into the lungs. People may need to eat foods with only certain textures or drink thickened liquids to help reduce the risk of aspiration. A speech pathologist may teach people specific swallowing techniques (for example, swallowing while tucking the chin toward the chest) to reduce the risk of food and liquids going down into the lungs.

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