Why Are So Many People Developing Asthma—and What Can We Do About It?

A Deep Dive Into the Risk Factors Behind America's Most Common Chronic Lung Disease—for Asthma Awareness Month 2026

Key Takeaways

• 28.2 million Americans currently live with asthma—8.9% of adults and 6.7% of children. But the question nobody is asking loudly enough is: why are so many people developing it in the first place?

• Asthma is not something most people are born with. It develops—often in the first years of life, shaped by genetics, environment, and exposures that begin before birth.

• The risk factors are real, many are preventable, and awareness of them can make a difference—especially for parents of young children.

• Adult asthma prevalence has increased significantly from 2013 through 2021—meaning this is not just a childhood disease, and it is not getting better on its own.

• The air inside your home is one of the most significant and most modifiable risk factors for both developing and worsening asthma—and it is the one most families never think to address.

Asthma Awareness Month 2026: Let's Talk About Why It Happens

Every May, the conversation about asthma follows a predictable script: know your triggers, carry your inhaler, check the air quality index before you go outside. All important. None of it wrong.

But this Asthma Awareness Month, we want to ask a harder question—one that gets asked far less often than it should be:

Why are so many people developing asthma to begin with?

The yearly cost of asthma in the United States is approximately $82 billion. 44% of children with asthma have uncontrolled asthma. 1.4 million emergency department visits per year are attributed to asthma as a primary diagnosis.

These numbers do not reflect a disease that is being prevented. They reflect a disease that is being managed—imperfectly, expensively, and often without ever addressing what caused it. If we want to actually move the needle on asthma, we have to talk about risk factors. Not just what triggers an attack, but what causes the disease to develop in the first place.

First: What Is Asthma, and What Is Actually Happening in the Body?

Asthma is a chronic inflammatory disease of the airways. The word "inflammatory" is important—asthma is not simply a mechanical problem with the lungs. It is an immune system problem that manifests in the lungs.

In a person with asthma, the airways are in a state of chronic low-grade inflammation. When they encounter a trigger—dust mites, mold spores, smoke, cold air, a chemical fume—that inflammation flares. The airway lining swells. Mucus production increases. The muscles surrounding the airways contract, narrowing the passage through which air must flow. The result is the familiar constellation of symptoms: tightening in the chest, wheezing, coughing, and shortness of breath.

In a mild episode, a rescue inhaler relaxes those airway muscles and the symptoms resolve. In a severe episode—an asthma attack—the narrowing is severe enough to be life-threatening.

What makes asthma particularly complex is that it is not one disease. It is an umbrella term covering multiple subtypes, with different underlying immune mechanisms, different triggers, different ages of onset, and different responses to treatment. The vast majority of childhood-onset asthma manifests as an allergic phenotype, while there is a predominance of the non-allergic phenotype in adult-onset asthma.

Understanding this distinction—allergic versus non-allergic, childhood-onset versus adult-onset—matters enormously for understanding why people develop it and what can be done to prevent it.

• 28.2 million Americans currently have asthma

• 6.7% of children under 18—roughly 1 in 15

• 8.9% of adults—nearly 1 in 11

• 44% of asthmatic children have uncontrolled asthma

• $82 billion annual economic burden to the US

• 1.4 million ER visits per year—asthma as primary diagnosis

• 5.2 million school days lost annually

• Adult asthma prevalence is rising—even as childhood asthma rates have slightly declined

• Asthma is the #1 chronic illness in American children

Babies Are Not Born With It—So How Does It Develop?

Most children with asthma are not born with it. The disease develops—usually in the first few years of life—through a complex interaction of genetic predisposition and environmental exposure. Understanding that interaction is the key to prevention.

The Genetics: Family History Matters—A Lot

Genetics play a significant role in asthma risk, but they do not determine destiny. Having a parent or sibling with asthma substantially increases a child's likelihood of developing it—and the connection extends beyond asthma specifically. Large-scale genome-wide association studies have discovered a number of highly shared genetic susceptibility sites among asthma, allergic rhinitis, and atopic dermatitis, suggesting these three allergic diseases share underlying biological pathways.

In practical terms: if one parent has asthma, a child's risk is meaningfully elevated. If both parents have asthma, the risk is significantly higher. And if a child has eczema or allergic rhinitis—two conditions in the same allergic "family"—their risk of developing asthma is also elevated.

But genetics explain only part of the picture. Asthma development in children is influenced by a myriad of factors, with both prenatal and postnatal exposures playing crucial roles in shaping respiratory health. This means that even children with no family history can develop asthma if their early environment is working against them—and children with a strong genetic predisposition may never develop it if their environment is protective.

The Risk Starts Before Birth

One of the most important and underappreciated insights from recent research is that asthma risk is not just a childhood story. It begins in pregnancy.

Maternal smoking during pregnancy is a well-established prenatal risk factor for childhood asthma. Exposure to tobacco smoke in utero can lead to impaired lung development, altered immune responses, and increased susceptibility to respiratory infections, all of which contribute to the development of asthma in childhood. Additionally, maternal smoking may induce epigenetic changes in the developing fetus, further increasing the risk of asthma later in life.

Paternal smoking matters too—perhaps in ways that surprise many people. Evidence indicates that paternal prenatal smoking can result in epigenetic alterations that heighten the susceptibility of their progeny to asthma, with a comprehensive investigation encompassing 24,168 parents finding a positive correlation between paternal smoking prior to conception and an elevated likelihood of asthma in their offspring.

Maternal air pollution exposure during pregnancy has also emerged as a critical factor. Research presented at ATS 2025 found that offspring of mice whose mothers were exposed to air pollution during pregnancy showed more severe asthma symptoms as adults, with thousands of genes in the lungs of these offspring expressed differently—suggesting an epigenetic "memory effect" of prenatal air pollution exposure that persists into adulthood. Notably, the levels of air pollution tested met WHO air quality guidelines for "safe," prompting concerns that current standards may not fully protect pregnant individuals and future generations.

Maternal diet during pregnancy also plays a role. High-fat diets rich in saturated fats have been associated with increased airway inflammation and asthma risk in children, while vitamin D deficiency has been implicated in asthma pathogenesis, with supplementation showing potential benefits in reducing asthma exacerbations.

The message for expectant parents is clear: the respiratory health of your child is being shaped right now, during pregnancy, by what you breathe, what you eat, and what you are exposed to.

Prenatal Asthma Risk Factors"

Risk factors that begin during pregnancy:

• Maternal smoking—impairs fetal lung development and alters immune programming

• Paternal smoking—epigenetic changes passed to offspring even before conception

• Maternal air pollution exposure—creates lasting epigenetic changes in offspring lung function

• Vitamin D deficiency—linked to increased wheezing and asthma in offspring

• High saturated fat diet—associated with increased airway inflammation in children

• Prenatal stress—identified as a significant modifiable risk factor for asthma development

• Family history of asthma, eczema, or allergic rhinitis—strong genetic predisposition

• Preterm birth and low birth weight—significantly elevated asthma risk

• Cesarean section delivery—associated with altered immune development and higher asthma rates

When Are Children Typically Diagnosed—and Who Is Most at Risk?

Most childhood asthma is diagnosed between the ages of 2 and 6, though many children show early signs—recurrent wheezing, persistent cough, frequent respiratory infections—before a formal diagnosis is made. Wheezing in infancy is common and often transient, but when it recurs and persists, it frequently represents the early stages of asthma.

Gender is a significant variable. Childhood asthma is more common in boys, while adult asthma is more common in women, and the reversal of this sex difference in prevalence occurs around puberty, suggesting sex hormones may play a role in the etiology of asthma.

Ethnicity and race are also significant—and the disparities are stark. Prevalence of current asthma is notably higher among non-Hispanic Black children at 12.5% and Black adults at 10.6%, compared to 5.7% and 8.2% respectively among non-Hispanic White people. Black people in the US are nearly 6 times more likely than White people to visit the emergency department due to asthma. These disparities are not simply genetic—they reflect the compounding effects of environmental exposures, housing quality, air pollution burden, access to healthcare, and socioeconomic stress.

The Environmental Factors: Where Things Get Urgent

It’s been said: genetics load the gun; environment pulls the trigger. The environmental factors that drive asthma development are numerous—and several of them are preventable.

Early-Life Viral Infections

The early-life risk factors with the greatest population attributable fraction—meaning those most likely to have a large modifiable impact on asthma development—included acute viral respiratory tract infections, antibiotic use, inadequate physical activity, prenatal stress, secondhand smoke exposure, and allergic sensitization.

Respiratory syncytial virus (RSV) in particular is among the strongest predictors of future asthma risk in children. Early, severe RSV infection appears to prime the airway immune response in ways that set the stage for asthma later in childhood. This is an area of active research—and one reason the recent development of RSV immunoprophylaxis for infants is seen as potentially significant for asthma prevention as well.

Mold in Homes and Schools

Residential exposure to mold in early life has been dose-dependently associated with persistent wheezing later in childhood, and increased long-term exposure to dampness has been associated with development of asthma.

A nationwide US study found that household mold is associated with current asthma among children, independent of other major risk factors including obesity.

Up to 25% of patients with asthma demonstrate sensitization to common indoor molds such as Alternaria and Aspergillus species, which may contribute to disease activity.

Schools are a particularly important and underexamined exposure site. Children spend approximately six to eight hours per day in school buildings—many of which are aging, inadequately ventilated, and chronically moisture-damaged. Mold in school buildings is widespread, frequently unreported, and almost never linked publicly to the asthma rates of the children inside those buildings.

Pesticides and Agricultural Exposure

This is the connection that our friends at Change the Air Foundation and clinicians like Dr. Lyn Patrick have been drawing attention to—and the research backs it up.

A 2024 study found that approximately 62% of children aged 5–12 years lived within 400 meters of at least one pesticide application within the prior 12 months, and that exposure to pesticides within 400 meters of children's residences was significantly associated with wheezing.

A systematic review found that 18 out of 25 pesticide studies reported a positive association between exposure to pesticides and adverse childhood respiratory health effects, and 11 out of 12 studies on agricultural burning also reported positive associations with adverse respiratory health in children.

The Midwest—one of the most heavily agricultural regions of the country—reflects this pattern in its asthma rates. Pesticide drift, agricultural burning, and the concentration of farming operations near residential areas creates a chemical environment that children's developing lungs and immune systems are not equipped to handle.

Urban Smog and Air Pollution

Indoor air can be up to five times more polluted than outdoor air—but outdoor air matters too, particularly in cities with high traffic density, industrial activity, or geography that traps smog.

Cities with historically poor air quality show elevated asthma rates, particularly in communities located near highways, ports, or industrial facilities. The cumulative effect of breathing polluted outdoor air—nitrogen dioxide, particulate matter, ozone, sulfur dioxide—on a developing child's airway is substantial.

Allergies, Food Sensitivities, and the Autoimmune Connection

Asthma does not exist in isolation. It is part of what researchers call the "atopic march"—a progression that often begins with eczema in infancy, advances to food allergies and allergic rhinitis in early childhood, and culminates in asthma. A strong genome-wide genetic correlation between asthma and other allergic diseases including allergic rhinitis and atopic dermatitis has been found, with these three conditions sharing underlying biological pathways.

The immune system in allergic individuals is wired to overreact—to produce inflammatory responses to things that are not genuinely dangerous. In asthma, that overreaction targets the airway. In eczema, it targets the skin. In allergic rhinitis, it targets the nasal passages. They are expressions of the same underlying immune dysregulation.

According to the Asthma and Allergy Foundation of America, allergies trigger at least 30% of adult asthma cases.

The hygiene hypothesis—the idea that children raised in overly sterile environments develop immune systems that overreact to harmless stimuli—offers one partial explanation for why asthma and allergies are more prevalent in higher-income, more urbanized populations. Unlike industrial agricultural settings — where chemical exposure can heighten asthma risk — children raised on small family farms, with daily contact with animals, gardens, and soil, tell a different story. 

Those who grow up with early, routine exposure to a diverse range of microorganisms consistently show lower rates of asthma. Research finds that children living in these environments had lower prevalence of asthma and atopy, with greater microbial diversity inversely associated with asthma risk — a reminder that not all environmental exposure works against us. Some of it, it turns out, is exactly what the immune system needs.

This does not mean parents should seek out dirt—it means that the gut microbiome, established in early life through diverse environmental exposures, plays a profound role in calibrating the immune system. Antibiotic overuse in infancy, formula feeding, C-section delivery, and overly sanitized environments may all contribute to immune dysregulation that manifests as allergy and asthma later in life.

Prenatal:

• Maternal and paternal smoking

• Air pollution exposure during pregnancy

• Vitamin D deficiency

• High saturated fat diet

Early childhood:

• Severe RSV or respiratory infections

• Exposure to household mold and dampness

• Living near agricultural pesticide use

• Secondhand smoke exposure

• Urban air pollution / traffic-related particulate matter

• Antibiotic overuse disrupting gut microbiome

• Lack of breastfeeding (breastfeeding is protective)

• Obesity in early childhood

Ongoing:

• Dust mite sensitization in the home

• Pet dander without early exposure balance

• Cockroach allergen (particularly in urban housing)

• VOCs from cleaning products and synthetic fragrances

• Gas stove NO2 exposure

• Mold in schools and homes

It's Not Just Children: Adult-Onset Asthma Is Increasing—and It's Harder to Treat

The assumption that asthma is primarily a childhood disease is outdated. Nearly 23 million US adults ages 18 and older have asthma. Asthma is more common in female adults than male adults—around 11.0% of female adults have asthma, compared to 6.8% of male adults.

Asthma that starts in adulthood differs from childhood-onset asthma in that it is often non-atopic, more severe, and associated with a faster decline in lung function.

Adult-onset asthma symptoms tend to be harder to control. For these reasons, adults with asthma have a higher risk of flare-ups and even hospitalization, and the death rate for adult-onset asthma is far higher than the death rate for childhood asthma.

Why does asthma develop in adults who had none of the typical childhood risk markers? The triggers are different. Common reasons for adult asthma include constant exposure to an allergen, obesity and the systemic inflammation it produces, hormonal changes in women during pregnancy and menopause, and occupational exposures to chemical irritants.

Workplace chemical exposure—from cleaning products, industrial solvents, paints, hair salon chemicals, agricultural chemicals—is a significant and underappreciated driver of adult-onset asthma. For adults who spend 40 hours a week in a poorly ventilated workspace with chemical exposures, the cumulative burden on the airway is substantial.

It is also worth noting that many adults diagnosed with asthma for the first time were not truly disease-free before. Most patients with asthma, regardless of their age of onset, seem to have had some form of airway symptoms during childhood—suggesting that asthma inception and related pathophysiological processes are very likely to occur in the first years of life even when formal diagnosis comes later. What looks like new-onset adult asthma may often be the re-emergence of a subclinical process that was there all along.

What Can Parents Do? A Practical Prevention Guide

Awareness without action is just anxiety. Here is what the research supports for reducing asthma risk in children:

During pregnancy:

• Do not smoke—and ask partners and household members to stop as well

• Minimize exposure to air pollution—avoid heavy traffic areas, use HEPA filtration at home

• Optimize vitamin D levels—ask your OB or midwife about supplementation

• Eat a diet rich in omega-3 fatty acids, fruits, and vegetables

• Reduce exposure to household chemicals and synthetic fragrances

In infancy and early childhood:

• Breastfeed if possible—breastfeeding is consistently identified as a protective factor against asthma

• Avoid unnecessary antibiotic use—preserving the gut microbiome matters

• Address mold in the home promptly—do not paint over it, remediate it properly

• Keep the bedroom clean of dust mites—allergen-proof mattress covers, hot water washing of bedding

• Run an air purifier with genuine HEPA and activated carbon filtration in the child's bedroom—particularly if there is family history of asthma, allergy, or eczema

Ongoing:

• Switch to fragrance-free, non-toxic cleaning products—synthetic fragrance chemicals are documented asthma triggers

• Address any visible mold or moisture problems in the home immediately

• If you live near agricultural land, consider air filtration during high pesticide application seasons

• Know your child's allergy status—untreated environmental or food allergies increase asthma risk

• Keep pets out of the bedroom—even beloved pets contribute meaningfully to airborne allergen load in sleeping spaces

Austin Air: The Air Filtration Standard for Asthma Families

We will go deeper into the clinical research in a dedicated blog later this month. But the short version is this: Austin Air is the only air purifier company to have undergone seven independent clinical trials with major research institutions—including Cincinnati Children's Hospital and Johns Hopkins University—and to have achieved positive results in every single one.

The landmark Cincinnati Children's Hospital trial, published in Pediatrics, found that running Austin Air HealthMate units in asthmatic children's bedrooms and main living areas resulted in approximately 42 fewer unplanned doctor or ER visits per year compared to controls.

The reason Austin Air works for asthma—where many competitors fall short—is filtration depth. Medical-grade HEPA captures particles down to 0.1 microns: mold spores, dust mite debris, pet dander, particulate matter. And 15 pounds of activated carbon and zeolite captures the gases and VOCs—the chemical asthma triggers that pass straight through HEPA-only filters.

For asthma prevention and management, the bedroom comes first. That is where your child spends eight hours every night breathing the same air. The Austin Air Bedroom Machine was designed specifically for that environment. From there, our whole-home bundles extend the same protection to every room where your family spends time.

Explore the Breathe Better Toolkit and our whole-home asthma bundles at austinairsystems.com.

The Bottom Line

Asthma is not inevitable. It develops—shaped by genetics that we cannot change and by environmental exposures that, in many cases, we absolutely can.

This Asthma Awareness Month, the most important thing we can do is widen the conversation beyond inhalers and triggers to the upstream question of why 28 million Americans are developing this disease in the first place. The answers are in the data: prenatal exposures, early-life indoor air quality, pesticides, mold, allergen sensitization, and an immune system that was never given the inputs it needed to calibrate correctly.

Some of those risk factors are beyond any individual family's control. But many are not. And for families who want to do everything possible to protect the children in their care—especially those with a family history of asthma, eczema, or allergic rhinitis—the indoor environment is the most powerful lever available to you.

The air in your home matters. It is where your child sleeps, breathes, grows, and develops. Make it count.

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Last updated 28 April, 2026