Aspiration pneumonia is inflammation of the lungs and airways to the lungs (bronchial tubes) from breathing in foreign material.

Aspiration pneumonia is caused by breathing foreign materials (usually food, liquids, vomit, or fluids from the mouth) into the lungs. This may lead to:

• A collection of pus in the lungs (lung abscess)
• An inflammatory reaction
• A lung infection (pneumonia)

Aspiration of foreign material into the lungs can be caused by:

• Anesthesia
• Coma
• Decreased or absent gag reflex in people who are not alert (unconscious or semi-conscious)
• Dental problems
• Disorders that affect normal swallowing
• Disorders of the esophagus (esophageal stricture, gastroesophageal reflux)
• Excessive alcohol use
• Medications that affect alertness
• Old age
• Sedatives

Acidic material that is breathed into the lungs can cause severe lung injury. However, it may not necessarily lead to pneumonia.