Merck Manual

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Some Causes and Features of Wheezing

Some Causes and Features of Wheezing


Common Features*



Sometimes symptoms of an upper respiratory infection (such as a stuffy nose)

Usually no known history of a lung disorder

A doctor's examination

Wheezing that starts suddenly, usually within 30 minutes of exposure to a known or potential allergen such as pollen

Often a stuffy nose, hives, itchy eyes, and sneezing

A doctor's examination

Usually a history of asthma

Wheezing that starts spontaneously or after exposure to specific stimuli (such as pollen or another allergen, an upper respiratory infection, cold, or exercise)

A doctor's examination

Sometimes one or more of the following tests:

  • Tests to evaluate how well the lungs are functioning ( pulmonary function tests Pulmonary Function Testing (PFT) Pulmonary Function Testing (PFT) )

  • Measurement of peak air flow (how fast air can be exhaled)

  • Measurement of lung function before and after exercise or administration of methacholine (a drug that narrows airways)

  • Sometimes use of bronchodilators (drugs that widen airways) to see whether symptoms go away

Bronchiolitis Bronchiolitis (infection of the lower respiratory tract)

In children under 18 months old

Usually occurring from November to April in the Northern Hemisphere

Usually symptoms of an upper respiratory infection (such as a stuffy nose and fever) and rapid breathing

A doctor's examination

In middle-aged or older people

In people who already have COPD

Usually a history of extensive smoking

Labored breathing

A chest x-ray

Drugs (such as ACE inhibitors, beta-blockers, aspirin, and other NSAIDs)

In people who have recently started using a new drug, most often in those with a history of airway obstruction (as occurs in asthma)

A doctor's examination

A foreign object that has been inhaled

High-pitched wheezing or cough that starts suddenly in people (typically infants or young children) without any symptoms of an upper respiratory infection, fever, or other symptoms of illness

A chest x-ray or CT of the chest

GERD Gastroesophageal Reflux Disease (GERD) Gastroesophageal Reflux Disease (GERD) with repeated reflux of stomach contents into the lungs (chronic aspiration)

Chronic or recurring wheezing

Often burning pain in the chest (heartburn) or abdomen that tends to worsen after eating certain foods, while exercising, or while lying flat

A sour taste, particularly after awakening


A cough that occurs in the middle of the night or early morning

No symptoms of an upper respiratory infection or allergy

Sometimes only a doctor's examination

Sometimes use of drugs that suppress acid, such as a histamine-2 (H2) blocker or proton pump inhibitor, to see whether symptoms go away

Sometimes insertion of a flexible viewing tube into the esophagus and stomach ( endoscopy Endoscopy )

Sometimes placement of a sensor in the esophagus to monitor acidity (pH) for 24 hours

Usually swelling (edema) of the legs

Shortness of breath that worsens while lying flat or that appears 1–2 hours after falling asleep

Sounds suggesting fluid in the lungs, heard through a stethoscope

A chest x-ray

Sometimes a blood test to measure a substance that is produced when the heart is strained called brain natriuretic peptide (BNP)

Irritants that are inhaled

Wheezing that starts suddenly after exposure to irritants at work (occupational exposure) or inappropriate use of cleaning products

A doctor's examination

Wheezing while inhaling and exhaling, especially in people with risk factors for or signs of cancer (such as a history of smoking, night sweats, weight loss, and coughing up blood)

A chest x-ray or CT of the chest

* Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present.

† Doctors usually measure the oxygen level in blood with a sensor placed on a finger (pulse oximetry). A chest x-ray is usually taken unless the person's symptoms are clearly a flare-up of an already diagnosed chronic disorder.

ACE = angiotensin-converting enzyme; COPD = chronic obstructive pulmonary disease; CT = computed tomography; GERD = gastroesophageal reflux disease; NSAIDs = nonsteroidal anti-inflammatory drugs.