Childhood asthma is a chronic lung disease that affects millions of children worldwide, causing airways to swell and narrow, making it difficult to breathe. When children have asthma, their airways become easily inflamed when exposed to certain triggers such as pollen, colds, or exercise. This condition can cause irritating daily symptoms that interfere with play, sports, school, and sleep, but with proper management, most children can lead normal, active lives.

How Common Is Childhood Asthma?

Asthma is the leading cause of chronic illness in children, affecting approximately 7.5 million children in the United States alone.^[1] Globally, the disease touches the lives of millions of young people, making it one of the most widespread childhood health conditions. The rate of asthma in children has been steadily increasing over recent decades, with studies showing that the prevalence increased by 160 percent between 1980 and the mid-1990s, particularly among children under four years old.^[2]

Most children who develop asthma experience their first symptoms by age 5.^[3] Nearly half of all infants wheeze during their first year of life, though most will not go on to develop persistent asthma.^[4] The condition is not only common but also represents one of the main reasons children miss school and one of the primary causes for parents to miss work. Asthma is responsible for approximately 3 million physician visits, 570,000 emergency department visits, 164,000 hospital stays, and 10 million missed school days per year in the United States alone.^[5]

The burden of childhood asthma does not affect all groups equally. Black children in the United States are 26 percent more likely to have asthma compared to white children and experience more severe disability and more frequent hospitalizations.^[6] Black children are also four to six times more likely to die from asthma compared to their white peers. Additionally, Native American and Puerto Rican children face increased risk compared to white children, highlighting important disparities in how this disease affects different communities.^[7]

What Causes Childhood Asthma?

Researchers do not fully understand the exact cause of asthma, but the disease appears to develop through a complex interaction between genetic factors and environmental influences.^[8] Asthma most often begins during childhood when a child’s immune system is still developing and maturing. The airways of children with asthma become chronically inflamed, which means they are persistently swollen and irritated. This inflammation makes the airways prone to overreacting when exposed to certain triggers.

When inflammation occurs, several things happen in the airways. Mast cells, which are special cells involved in immune responses, release substances such as histamine, leukotrienes, prostaglandins, and thromboxanes.^[9] These substances cause blood vessels to widen, tissues to swell, and airways to constrict or narrow. Leukotrienes are particularly powerful inflammatory substances, being approximately 1,000 times more potent than histamines in triggering an inflammatory response.

The inflammatory process in asthma occurs in two phases. During the early phase, the immediate release of these chemical mediators leads to rapid symptoms. During the late phase, other immune cells including eosinophils, basophils, lymphocytes, and additional mast cells prolong the inflammation.^[10] Over time, chronic inflammation may result in permanent changes to the airways, including thickening of the smooth muscle around the airways, increased responsiveness to triggers, and increased collagen deposits beneath the lining of the airways, all of which further narrow the breathing passages.

Risk Factors for Developing Asthma

Several factors increase the likelihood that a child will develop asthma. Understanding these risk factors can help parents and healthcare providers identify children who may be at higher risk and monitor them more closely for early signs of the disease.

Family history and genetics play a significant role. Children are more likely to develop asthma if one of their parents has it, especially if it is the mother.^[11] If both parents have asthma or allergies, the risk increases even further. This genetic component suggests that certain inherited traits make some children’s airways more prone to inflammation and hyperresponsiveness.

Allergies are closely linked to asthma. Children who have other allergic conditions such as eczema (a skin condition causing itchy, inflamed skin), hay fever, or food allergies face increased risk. Many children with asthma have what is called allergic asthma, meaning their symptoms are triggered by exposure to allergens such as dust mites, mold, pet dander, pollen from grasses and trees, or waste from pests like cockroaches and mice.^[3]

Environmental exposures significantly affect asthma risk. Being exposed to secondhand smoke during pregnancy or early childhood substantially increases a child’s chances of developing asthma.^[12] Living in areas with high air pollution also raises risk. Interestingly, researchers believe that some modern environmental changes may partly explain why more children are developing asthma, including increased exposure to allergens, toxins, and secondhand smoke, combined with decreased exposure to childhood illnesses that might help build immune systems and lower rates of breastfeeding, which provides important immune system support to babies.^[2]

Other risk factors include obesity, which has been linked to both increased likelihood of asthma diagnosis and more severe disease with more frequent symptoms.^[13] Frequent viral respiratory infections during early childhood also increase risk. Additionally, children who were born with low birthweight or who experienced prenatal exposure to tobacco smoke face elevated risk.^[14] Socioeconomic challenges represent another major risk factor, including limited access to medical care, living conditions that negatively impact respiratory health such as exposure to mold or cockroaches, and less flexibility for attending healthcare appointments.

Recognizing Symptoms of Childhood Asthma

The symptoms of childhood asthma can vary widely from one child to another, and even the same child may experience different symptoms during different episodes. Some children have only mild, occasional symptoms, while others face daily challenges that significantly impact their quality of life.^[1]

Common symptoms include a whistling or wheezing sound when breathing out. Wheezing is a high-pitched sound caused by air trying to move through narrowed airways. However, not all children with asthma wheeze, and wheezing can also be caused by other conditions, so it is not exclusive to asthma.^[15] Some children experience shortness of breath or rapid breathing, which may be associated with exercise or physical activity. When breathing becomes difficult, a child may feel chest congestion, tightness, or discomfort. Young children might describe this as their chest “hurting” or “feeling funny.”

Coughing represents one of the most common symptoms and can sometimes be the only sign of asthma. This cough often gets worse when a child has a viral infection, during sleep, while exercising, or when exposed to cold air.^[16] The coughing may be constant or may come and go. Some children have what is called cough variant asthma, where chronic cough that doesn’t go away is the primary symptom.

Additional signs that parents should watch for include trouble sleeping due to shortness of breath, coughing, or wheezing. Children may experience delayed recovery or develop bronchitis (inflammation of the breathing tubes) after respiratory infections. Some children show less energy during play or may avoid sports and social activities because physical activity makes their symptoms worse. They might complain of fatigue, which can result from poor sleep caused by nighttime symptoms. Young children may appear irritable, and infants might have trouble feeding or make grunting sounds during feeding.^[2]

Parents should also look for physical signs that a child is working harder to breathe. Retractions occur when the skin between the ribs, on top of the ribs, or below the ribs pulls inward when a child tries to breathe out, indicating they are struggling to move air through narrowed airways.^[3] Some children breathe faster than normal or have difficulty talking in long sentences when their asthma is acting up.

Preventing Asthma and Reducing Attacks

While there is no proven way to prevent a child from developing asthma entirely, several strategies can reduce the risk of developing the disease or decrease the frequency and severity of asthma attacks in children who already have the condition.

Avoiding tobacco smoke represents one of the most important preventive measures. Both prenatal and postnatal exposure to tobacco smoke increase asthma risk.^[17] Parents should avoid smoking during pregnancy and ensure their children are not exposed to secondhand smoke or vape chemicals after birth. Smoke and vaping products are among the most common irritants for people with asthma and can lead to permanent lung damage.

Breastfeeding may offer some protection. Lower rates of breastfeeding have been identified as one factor potentially contributing to rising asthma rates, as breast milk provides important immune system substances to babies.^[2] Maintaining a healthy body weight also matters, as obesity has been linked to increased asthma risk and more severe disease.

For children already diagnosed with asthma, preventing attacks focuses on identifying and avoiding individual triggers. Common triggers include environmental allergens such as pollen, dust mites, mold, and pet dander. Parents can reduce dust and mold in the home, especially in the child’s bedroom, by covering mattresses and pillows with protective dust-mite-proof covers, washing blankets and stuffed animals in hot water once per week, vacuuming frequently, and removing carpeting and rugs from the bedroom if possible.^[18]

Other triggers to avoid or manage include upper respiratory infections like colds and flu, which is why vaccination is important. Children with asthma should receive yearly flu vaccines and updated COVID-19 vaccines, as these viral infections can trigger serious asthma flare-ups.^[19] Weather changes, particularly to colder weather, can trigger symptoms, so having children wear scarves over their mouth and nose to warm inhaled air during cold weather can help. Strong smells from cooking spices or cleaning products, certain medications, and even strong emotional reactions such as crying, laughing, or yelling can trigger symptoms in some children.

Physical activity is important for children’s health and should not be avoided. However, some children experience exercise-induced asthma, where symptoms occur during or after physical activity.^[20] With correct management, including possibly taking medication before exercise and teaching children to breathe through the nose rather than the mouth during activity, most children with asthma can fully participate in sports and physical activities.

How Asthma Changes Normal Body Function

To understand how asthma affects children, it helps to know how normal breathing works. Airways are the tubes that carry air in and out of the lungs. When a child breathes in, air travels through the nose or mouth, down the windpipe, and into increasingly smaller tubes in the lungs called bronchi and bronchioles. At the end of these tubes are tiny air sacs where oxygen moves into the blood and carbon dioxide moves out to be exhaled.

In asthma, the airways are chronically inflamed, meaning they are persistently swollen and irritated. This inflammation causes several problems that make breathing difficult. First, the airways become hypersensitive or hyperresponsive, meaning they overreact to things that would not normally cause problems. When exposed to triggers, the smooth muscle wrapped around the airways tightens and squeezes, a process called bronchoconstriction. This squeezing narrows the airways, making it harder for air to flow through.

Second, the inflammation causes the lining of the airways to swell, further narrowing the passages through which air must travel. Think of trying to drink through a straw that has been pinched or squeezed—this is similar to what happens to airways during asthma.^[2] The narrowed airways make it difficult to get air into the lungs and, importantly, to get air back out, which is why wheezing when breathing out is such a common symptom.

Third, the inflamed airways produce extra thick, sticky mucus. This mucus can form plugs that further block the airways and make breathing even more difficult. The combination of muscle constriction, airway swelling, and mucus production creates the breathing difficulties experienced during an asthma attack or flare-up.

Over time, if asthma is not well controlled, chronic inflammation can lead to permanent changes in the airways called airway remodeling. The smooth muscle around the airways may thicken and enlarge, a process called hyperplasia. Increased collagen, a structural protein, may deposit beneath the basement membrane of the airway lining, causing further narrowing and stiffening of the airways.^[21] These structural changes can result in progressive loss of lung function and reduced lung growth in children, which is why proper asthma management during childhood is so important.

Asthma varies in severity and can change over time. Some children have only occasional mild symptoms, while others face persistent symptoms that significantly interfere with daily activities. The severity can also fluctuate, with periods of good control interrupted by flare-ups or attacks. These attacks may come on gradually over hours or days, or they may develop suddenly. During an attack, symptoms worsen considerably, and the narrowing of airways becomes more severe. Without proper treatment, severe attacks can become life-threatening, a condition called status asthmaticus, which requires emergency medical care.^[22]