Merck Manual

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Rebecca Dezube

, MD, MHS, Johns Hopkins University

Reviewed/Revised Nov 2023
Topic Resources

Causes of Wheezing

Wheezing results from a narrowing or partial blockage (obstruction) somewhere in the airways. The narrowing may be widespread (as occurs in asthma, chronic obstructive pulmonary disease [COPD], and some severe allergic reactions) or only in one area (as may result from a tumor or a foreign object lodged in an airway).

Common causes

Less common causes

Evaluation of Wheezing

A person with severe breathing problems (respiratory distress) is evaluated and treated at the same time.

The following information can help people decide when a doctor's evaluation is needed and help them know what to expect during the evaluation.

Warning signs

In people with wheezing, the following symptoms are of particular concern:

  • Labored breathing, weakening efforts to breathe, or a decreased level of consciousness

  • Swelling of the face and tongue

When to see a doctor

People with warning signs or shortness of breath should go to the hospital emergency department immediately, by ambulance if necessary. People who have wheezing that comes and goes and are not short of breath can usually wait a day or two.

What the doctor does

Doctors first ask questions about the person's symptoms and medical history and then do a physical examination. What doctors find during the history and physical examination often suggests a cause and the tests that may need to be done (see table ).

Doctors determine whether the wheezing is occurring for the first time or has occurred before. If the person has had wheezing before, they determine whether current symptoms are different in nature or severity.

Important clues to a diagnosis are

  • Whether the wheezing started suddenly or gradually

  • Whether it comes and goes

  • Whether any conditions (such as an upper respiratory infection, exposure to an allergen, particular seasons of the year, cold air, exercise, or feeding in infants) trigger it or make it worse

During the physical examination, doctors check the person's temperature and heart and breathing rates. Doctors look for signs of respiratory distress and examine the lungs, particularly how well air moves in and out and whether wheezing seems to affect all of the lungs or only part. A doctor is usually able to detect wheezing by listening with a stethoscope as the person breathes. Loud wheezing can be heard easily, sometimes even without a stethoscope. To hear mild wheezing, doctors may need to listen with a stethoscope while the person exhales forcefully. A persistent wheeze that occurs in one location in people who smoke may be due to lung cancer. Doctors also examine the heart, nose and throat, limbs, hands, feet, and skin.



Tests are done to assess severity, determine diagnosis, and identify complications. They usually include the following:

If wheezing has occurred for the first time, a chest x-ray may help in the diagnosis. In people with persistent, repeated, or undiagnosed episodes of wheezing, pulmonary function tests Pulmonary Function Testing (PFT) Pulmonary function tests measure the lungs' capacity to hold air, to move air in and out, and to absorb oxygen. Pulmonary function tests are better at detecting the general type and severity... read more Pulmonary Function Testing (PFT) may be needed to help measure the extent of airway narrowing and to assess the benefits of treatment. If asthma seems possible but is not confirmed by pulmonary function tests, people may be asked to exercise or be given a medication that triggers wheezing in people with asthma. If airway obstruction occurs, asthma can be confirmed.

If doctors suspect a tumor or a foreign object lodged in an airway, they can insert a flexible viewing tube (bronchoscope Bronchoscopy Bronchoscopy is a direct visual examination of the voice box (larynx) and airways through a viewing tube (a bronchoscope). A bronchoscope, a thin viewing tube with a light, has a camera at the... read more Bronchoscopy ) into the airway to identify the problem and, if it is an object, remove it.

Treatment of Wheezing

The main goal of treatment is to treat the underlying disorder.

Bronchodilators (which widen the airways), such as inhaled albuterol, can relieve wheezing. Corticosteroids, taken by mouth for a week or two, can often help relieve an acute episode of wheezing if it is due to asthma or chronic obstructive pulmonary disease.

Long-term control of persistent wheezing due to asthma may require inhaled corticosteroids, mast cell stabilizers, leukotriene modifiers, or immunomodulators (medications that affect the immune system—see table ).

Epinephrine injected under the skin (subcutaneously), antihistamines (such as diphenhydramine) given intravenously, corticosteroids (such as methylprednisolone), and albuterol taken through a nebulizer are given to people with a severe allergic reaction.

Key Points

  • Asthma is the most common cause, but not all wheezing is caused by asthma.

  • Wheezing that starts suddenly in people without a lung disorder may be due to inhalation of a foreign object or a toxic substance, an allergic reaction, or heart failure.

  • Pulmonary function tests can identify and measure airway narrowing.

  • Inhaled bronchodilators can help relieve wheezing, but the disorder causing wheezing must also be treated.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Accuneb, ProAir digihaler, Proair HFA, ProAir RespiClick, Proventil, Proventil HFA, Proventil Repetabs, Respirol , Ventolin, Ventolin HFA, Ventolin Syrup, Volmax, VoSpire ER
Adrenaclick, Adrenalin, Auvi-Q, Epifrin, EpiPen, Epipen Jr , Primatene Mist, SYMJEPI, Twinject
Aid to Sleep, Alka-Seltzer Plus Allergy, Aller-G-Time , Altaryl, Banophen , Benadryl, Benadryl Allergy, Benadryl Allergy Children's , Benadryl Allergy Dye Free, Benadryl Allergy Kapgel, Benadryl Allergy Quick Dissolve, Benadryl Allergy Ultratab, Benadryl Children's Allergy, Benadryl Children's Allergy Fastmelt, Benadryl Children's Perfect Measure, Benadryl Itch Stopping, Ben-Tann , Compoz Nighttime Sleep Aid, Diphedryl , DIPHEN, Diphen AF , Diphenhist, DiphenMax , Dytan, ElixSure Allergy, Genahist , Geri-Dryl, Hydramine, Itch Relief , M-Dryl, Nighttime Sleep Aid, Nytol, PediaCare Children's Allergy, PediaCare Nighttime Cough, PediaClear Children's Cough, PHARBEDRYL, Q-Dryl, Quenalin , Siladryl Allergy, Silphen , Simply Sleep , Sleep Tabs, Sleepinal, Sominex, Sominex Maximum Strength, Theraflu Multi-Symptom Strip, Triaminic Allergy Thin Strip, Triaminic Cough and Runny Nose Strip, Tusstat, Unisom, Uni-Tann, Valu-Dryl , Vanamine PD, Vicks Qlearquil Nighttime Allergy Relief, Vicks ZzzQuil Nightime Sleep-Aid
A-Methapred, Depmedalone-40, Depmedalone-80 , Depo-Medrol, Medrol, Medrol Dosepak, Solu-Medrol
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