Introduction

Asthma

Lower allergen levels in your home

• Vacuum carpets and upholstered furniture every week
• Wash sheets and blankets weekly in hot water
• Use special allergen-proof covers on mattresses and pillows
• Lower humidity levels indoors to 50%
• Limit pets' access to bedrooms
• Seal doors and windows
• Eliminate pests

Asthma is a chronic lung disease. Common symptoms are wheezing, coughing, chest tightness, and shortness of breath. During an asthma attack, the sides of the airways in lungs swell and the airways shrink, making it harder to breathe. Once considered rare, asthma is now a common disease in childhood. In the United States, nearly 25 million people have asthma, of which 5.5 million are children. ¹

Asthma is a major cause of missed time from school and work. Severe asthma attacks may require emergency room visits and hospitalizations, and they can be fatal. Asthma affects people of all races, sexes, and ages across every region of the U.S.

Asthma can be triggered by substances in the environment called allergens. Indoor allergens from dust mites, cockroaches, dogs, cats, rodents and molds are among the most important environmental triggers for asthma. ²

The National Heart, Lung, and Blood Institute of NIH issued the "2020 Focused Updates to the Asthma Management Guidelines: A Report from The National Asthma Education and Prevention Program Expert Panel Working Group". Report recommendations are designed to improve the care of people living with asthma and help primary care providers and specialists make informed decisions about asthma management. Asthma management guidance is provided for six areas:

• Using inhaled corticosteroids when needed for recurrent wheezing or persistent asthma.
• Using long-acting antimuscarinic agents (LAMAs) with inhaled corticosteroids for long-term asthma management. A LAMA is a bronchodilator, a medicine that helps keep airway muscles relaxed.
• Using allergy shots that contain small amounts of allergen to treat some people with allergic asthma.
• Using methods to reduce exposure to indoor asthma triggers.
• Using a fractional exhaled nitric oxide test to help manage asthma or confirm a diagnosis. Nitric oxide can increase when there is airway inflammation.
• Using bronchial thermoplasty to treat selected adults with persistent asthma. During this procedure heat is used to reduce muscle around the airways.

What Is NIEHS Doing?

NIEHS conducts and supports asthma research from basic studies in laboratories to human clinical trials. This research focuses on complex relationships among the environment and people’s genetics and immune system. Projects include:

• Development of sensors that measure personal environmental triggers of asthma.
• Clinical trials that examine if reduced indoor air pollution can improve asthma symptoms.
• Data science methods that combine environmental data gathered across the United States.

Asthma triggers in schools – NIEHS research demonstrates the importance of healthy school environments for reducing asthma risk. A study of inner-city students linked airborne mouse allergens in schools to increased asthma symptoms and decreased lung function in children. ³ This study suggests schools can take steps to improve air quality and help children who have asthma.

Indoor air pollution makes asthma worse – Indoor air pollutants are a major concern for lung health. NIEHS-funded research has shown that obese inner-city children living in homes with high levels of indoor air pollution may have worse asthma symptoms if they are also deficient in vitamin D. ⁴

Outside triggers of asthma – NIEHS-funded researchers found babies who breathe high levels of traffic-related air pollution were more likely to have persistent wheezing during childhood, and children exposed to high levels of traffic-related air pollution through age 7 were more likely to develop asthma. ⁵ Another NIEHS-funded study found that adolescents exposed to nitrogen dioxide, an indicator of traffic-related pollution, experienced shifts in hormone levels that affect their response to stress, suggesting a way that air pollution might make asthma worse. ⁶

Asthma and a changing climate – Climate can also affect the severity of asthma. Research has shown that natural disasters and extreme weather events can create conditions that may worsen asthma in several ways. ⁷ For example, heat and drought make wildfires more widespread and severe, leading to large spikes in air pollution. More intense rainfall and flooding can lead to mold growth in homes and commercial buildings. Prolonged drought can worsen dust storms in dry areas.

The genetics of asthma – Asthma often runs in families, which suggests that genetics plays a role in disease development. NIEHS researchers have shown that asthma patients with a specific genetic makeup who live close to a highway are more likely to have intense symptoms. ⁸ Another NIEHS study finds that certain indicators within DNA may predict a newborn’s risk of asthma. ⁹ This information may help researchers identify which children may develop asthma and how to develop a treatment for preventing the disease.

Asthma and the immune system – Although exposure to many microbes can benefit the immune system, exposures to others can be harmful. An NIEHS-funded study showed that children who live on traditional Amish farms, which use animals rather than machines, were less likely to have asthma. The researchers suggest that the rich microbial environment on Amish farms may help build a stronger immune response in those children. ¹⁰

Although exposure to some bacteria and similar microbes can benefit the immune system, exposure to others can be harmful. Scientists funded by NIEHS showed that children who were exposed to high levels of molds were more likely to have asthma at age 7. ¹¹ For children with allergies, the association was especially strong.

Further Reading

Stories from the Environmental Factor (NIEHS newsletter)

• NIH Statement on World Asthma Day (June 2021)
• Intense Allergic Asthma Mechanism Discovered in Mice (May 2021)
• Asthma Worsens When Signaling Pathway Is Triggered (March 2020)

Press Releases

• Oil Spill Cleanup Workers More Likely to Have Asthma Symptoms (August 17, 2022)
• Vitamin D May Protect Against Pollution-induced Asthma Associated Symptoms in Obese Children (March 8, 2019)
• Genetics and Pollution Drive Severity of Asthma Symptoms (Aug. 31, 2018)

Fact Sheets

2 pages

(226KB)

Asthma and Its Environmental Triggers

13 pages

(2MB)

Environment and Health A to Z

13

(1MB)

Medio Ambiente Y Salud, De La A a La Z

2

(263KB)

Preventing Asthma: A Landlord’s Guide to Property Maintenance for Healthy Homes

1

(92KB)

Thinking About Asthma: A Developer's Guide to Building a Healthy Home

2

(305KB)

El Asma Y Sus Desencadenantes Medioambientales

Podcasts

• The Shrinking Salton Sea and Children's Health (2022) – An NIEHS-funded project aims to understand how the rapid drying of the Salton Sea will impact local air pollution and affect children’s lung health. Their community-based approach educates and empowers residents to address local environmental health issues.
• Wildfire Smoke and Children's Health (2021) – Hear about children’s health risks from wildfire smoke exposure and advice for parents on how to keep kids safe during a wildfire event.

Additional Resources

• CDC Asthma Webpage – Information from the U.S. Centers for Disease Control and Prevention
• EPA Asthma Webpage – Information from the U.S. Environmental Protection Agency
• NHLBI Asthma Webpage – Information from the National Heart, Lung, and Blood Institute, part of the National Institutes of Health

Related Health Topics

• Air Pollution
• Allergens & Irritants
• Children's Health
• Climate Change
• Lung Diseases
• Mold
• Pet Allergens
• Pollen
• Smoking and Vaping