ASTHMA OVERVIEW

Asthma a chronic condition with symptoms of cough, wheezing, and/or difficulty breathing. These symptoms occur periodically, usually related to specific triggering events. Children with asthma have narrowed airways during these episodes; the narrowing is partially or completely reversible with asthma treatments. In addition, the airways of children with asthma are sensitive to a variety of stimuli, which may include viral illnesses (eg, the common cold), pollen, foods, or environmental conditions.

Asthma is the most common chronic disease in children in developed countries, affecting about 12 percent of children who are less than 18 years.

This topic review discusses the risk factors, symptoms, and diagnosis of asthma in children. Other topics about asthma in children are available separately. (See "Patient information: Asthma treatment in children" and "Patient information: How to use a peak flow meter" and "Patient information: Asthma inhaler techniques in children" and "Patient information: Trigger avoidance in asthma".)

Discussions of asthma and asthma treatments in adults are also available. (See "Patient information: Asthma treatment in adolescents and adults" and "Patient information: How to use a peak flow meter" and "Patient information: Asthma inhaler techniques in adults" and "Patient information: Trigger avoidance in asthma" and "Patient information: Pregnancy and asthma".)

ASTHMA RISK FACTORS

Asthma occurs when the small airways (bronchi) in the lungs become narrowed, which limits the flow of air out of the lungs (figure 1 and figure 2). This narrowing is usually reversible with treatment. Many different genetic and environmental factors can increase the risk of developing asthma, a few of which include:

• Pollution — Increased exposure to indoor and outdoor pollution may increase the risk of developing asthma.
• Exposure to tobacco smoke — Exposure to tobacco smoke during pregnancy and throughout childhood increase the risk of developing asthma.
• Family history — Children with a personal or family history of certain medical problems, such as asthma or eczema, are at increased risk of developing asthma.

However, not all children with asthma have known risk factors. In other words, even children who live in rural areas and whose parents do not smoke or have asthma can develop asthma. It is not clear if there are ways to reduce a child's risk of developing asthma.

ASTHMA SYMPTOMS

Coughing and wheezing — Symptoms of asthma in children include coughing and wheezing. The cough is usually dry and hacking and is most noticeable while the child sleeps and during early morning hours. It may also be triggered by exercise. Wheezing is a high-pitched noise that is usually heard when the child breathes out.

Coughing and wheezing tends to come and go during the day or night, depending upon the degree of airway narrowing in the lungs. Breathlessness, chest tightness or pressure, and chest pain may also occur. In addition to coughing or wheezing, a child may report that their chest or stomach hurts.

Asthma symptoms often develop in children before five years of age, although it is sometimes difficult to diagnose asthma in infants and toddlers.

Asthma triggers — Wheezing and coughing may occur at any time, but certain triggers are known to worsen asthma in many children.

Environmental conditions — In children with seasonal allergies, asthma symptoms may worsen during certain pollen seasons; trees pollinate in early spring, grasses in the late spring and summer, and weeds in the summer and fall. Symptoms can also flare as a result of mold growth (eg, during rainy seasons or in damp areas). Cold air, changes in barometric pressure, rain, or wind may cause increased asthma symptoms in certain people.

Upper respiratory infections — Viral upper respiratory infections (head and chest colds) are a common trigger of asthma in infants and young children. The most common viral infections include rhinovirus (the virus that causes most colds), respiratory syncytial virus, and influenza virus. (See "Patient information: The common cold in children" and "Patient information: Bronchiolitis in infants and children".)

Children with asthma should use their asthma treatments for cough and chest congestion rather than over-the-counter cold remedies.

Exercise — Narrowing of the airways can be triggered by exercise. This is called exercise-induced asthma (also called exercise-induced bronchoconstriction or EIB). Breathlessness, wheeze, and/or cough usually occur within five to ten minutes of the cool-down period after vigorous exercise. These symptoms tend to disappear after 20 to 45 minutes. Certain types of exercise (eg, swimming) are less likely to cause exercise-induced asthma than others (eg, running, skating), probably because they produce less airway cooling and drying. Short bursts of activity tend to be better tolerated than prolonged exercise. (See "Patient information: Exercise-induced asthma".)

Allergens — Indoor and outdoor allergens are an important trigger of childhood asthma, particularly for children older than three years of age. These include:

• House dust (ie, dust mites, cockroaches, mice droppings), particularly during vacuuming
• Animal exposures; cats and dogs are especially provocative but other furry animals (gerbils, rabbits, hamsters, etc) may be suspect, particularly if symptoms only occur in settings where these animals reside
• Pollens
• Molds
• Indoor pollutants (eg, paint, perfume, space heaters, gas stoves, room deodorizers)

If allergies are a possible cause of symptoms, skin or blood testing may be recommended. This can help to both identify triggers and determine the necessity of avoiding these triggers at home.

Symptom patterns — Children with chronic asthma may have one of several distinct patterns of symptoms:

• Intermittent asthma attacks with no symptoms between attacks
• Chronic symptoms with intermittent worsening
• Attacks that become more severe or frequent over time
• Morning "dipping", when symptoms worsen in the morning and improve as the day progresses
• Symptoms that begin during upper respiratory tract infections (eg, colds) and linger for several weeks after, with resolution during warmer weather.

Most asthma attacks develop slowly over a period of several days. Uncommonly, a severe attack can occur suddenly and with minimal warning.

ASTHMA DIAGNOSIS

The diagnosis of asthma in children requires a careful review of a child's current and past medical history, family history, and a physical examination. Specialized testing is sometimes needed to diagnose asthma and to rule out other possible causes of symptoms. Many children with asthma appear and sound completely normal.

Spirometry testing — The most accurate test for diagnosing asthma is spirometry. Spirometry measures the flow and volume of air generated after a child takes a very deep breath and then forcefully tries to blow all the air out of their lungs. The test is usually repeated after the child uses an asthma inhaler to confirm that the airflow obstruction is reversible (a feature of asthma).

Children younger than six years sometimes have a hard time following the instructions to perform spirometry. Testing of younger children and infants is described below (see 'Testing for young children' below).

Peak flow rate measurement — Peak expiratory flow rate (PEFR) measurements are generally easier for children between four and six years to perform. The test requires that the child take a very deep breath and then quickly blow out as hard as possible into a device called a peak flow meter. This is generally done three times, with the highest value recorded as the result. PEFR measurements are sometimes used in the daily home monitoring of people with asthma. (See "Patient information: How to use a peak flow meter".)

Challenge testing — If a child is thought to have asthma based upon the spirometry or PEFR result, a bronchial challenge may be recommended. This testing is designed to cause the airways to narrow in children with asthma. Testing is done in a specialized asthma testing center that is capable of providing emergency asthma care if needed.

• Methacholine or cold air challenge — During a methacholine challenge test, the child inhales a medication called methacholine. Methacholine causes the smooth muscles of the airways to constrict, which causes airway narrowing. The concentration of methacholine is increased slowly to determine if any of five doses will cause airway narrowing. Before and after each increased dose of methacholine, the child performs spirometry testing. The test is considered positive if there is a 20 percent decline in spirometry with any of the given doses.

At some asthma testing centers, a cold air challenge is done. In this test, the child breathes in cold air and then performs spirometry testing every few minutes for 20 minutes. The test is considered positive if there is a 20 percent decline in spirometry within 20 minutes of breathing in the cold air.

• Exercise challenge — During an exercise challenge, the child exercises for six to eight minutes, then stops and performs spirometry testing every few minutes for 20 minutes. The test is considered positive if there is a 10 percent decline in spirometry during the 20 minute cool down.

Additional testing — Other tests may be recommended to ensure that another condition is not the cause of a child's coughing or wheezing. This may include a chest x-ray, sweat chloride test (for cystic fibrosis), barium swallow (for gastroesophageal reflux), or skin testing (for allergies).

In some children, skin or blood testing for allergies may be recommended. (See "Patient information: Food allergy symptoms and diagnosis".)

Testing for young children — Infants and children younger than four years are usually not able to perform spirometry or peak expiratory flow rate testing. In most cases, a healthcare provider will recommend a trial of treatment to confirm the diagnosis.

ASTHMA IN ADULTHOOD

Many parents wonder if their child will "outgrow" their asthma over time. Children do experience complete remission more frequently than adults; 30 to 70 percent of children with asthma are markedly improved or have no signs of asthma by early adulthood. Children with more severe asthma are more likely to continue to have asthma as adults.

Having asthma does not typically affect the length of a person's life. However, a small percentage of people with asthma develop permanent changes in lung function that worsen over time. It is not known why this happens in some people and not in others. Factors that are believed to increase this risk include exposure to tobacco smoke, severe allergies, and severe and persistent asthma symptoms.

ASTHMA TREATMENT

The treatment of asthma in children is discussed in a separate topic review. (See "Patient information: Asthma treatment in children".)

WHERE TO GET MORE INFORMATION

Your child's healthcare provider is the best source of information for questions and concerns related to your child's medical problem.

This article will be updated as needed every four months on our Web site (www.uptodate.com/patients).

Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information

Patient information: A guide to asthma
Patient information: Asthma treatment in children
Patient information: How to use a peak flow meter
Patient information: Asthma inhaler techniques in children
Patient information: Trigger avoidance in asthma
Patient information: Asthma treatment in adolescents and adults
Patient information: Asthma inhaler techniques in adults
Patient information: Pregnancy and asthma
Patient information: The common cold in children
Patient information: Bronchiolitis in infants and children
Patient information: Exercise-induced asthma
Patient information: Food allergy symptoms and diagnosis

Professional level information

Acute asthma exacerbations in children: Inpatient management
Acute asthma exacerbations in children: Outpatient management
Acute severe asthma exacerbations in children: Intensive care unit management
An overview of asthma management
Anticholinergic agents in the management of acute exacerbations of asthma
Approach to wheezing in children
Chronic asthma in children younger than 12 years: Controller medications
Chronic asthma in children younger than 12 years: Definition, epidemiology, and pathophysiology
Chronic asthma in children younger than 12 years: Evaluation and diagnosis
Chronic asthma in children younger than 12 years: Quick-relief agents
Exercise-induced bronchoconstriction
Natural history of asthma
Risk factors for asthma
The impact of breastfeeding on the development of allergic disease
Patient information: A guide to asthma

The following organizations also provide reliable health information.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• National Heart, Lung, and Blood Institute

      (www.nhlbi.nih.gov/)

• National Lung Health Education Program

      (www.nlhep.org)

• American Lung Association

      (www.lungusa.org)

• American Academy of Allergy, Asthma, and Immunology

      (www.aaaai.org/patients.stm)

• American College of Allergy, Asthma, and Immunology

      (www.acaai.org/public/)

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