Accessible Search Form           Advanced Search

  • PRINT PAGE  |  PRINT ENTIRE TOPIC  |  SHARE

What Causes Asthma?

The exact cause of asthma isn't known. Researchers think some genetic and environmental factors interact to cause asthma, most often early in life. These factors include:

  • An inherited tendency to develop allergies, called atopy (AT-o-pe)
  • Parents who have asthma
  • Certain respiratory infections during childhood
  • Contact with some airborne allergens or exposure to some viral infections in infancy or in early childhood when the immune system is developing

If asthma or atopy runs in your family, exposure to irritants (for example, tobacco smoke) might make your airways more reactive to substances in the air.

Some factors might be more likely to cause asthma in certain people than in others. Researchers continue to explore what causes asthma.

The Hygiene Hypothesis

One theory researchers have for what causes asthma is called the hygiene hypothesis. They believe that our Western lifestyle—with its emphasis on hygiene and sanitation—has resulted in changes in our living conditions and an overall decline in infections in early childhood.

Many young children no longer have the same types of environmental exposures and infections as children did in the past. This affects the way that young children's immune systems develop during very early childhood, and it may increase their risk for atopy and asthma. This is especially true for children who have close family members with one or both of these conditions.

Rate This Content:

  
previous topic next topic

Featured Video


Hard to breathe: NHLBI researchers seek treatments for severe asthma

Join the NHLBI in Observing Asthma Awareness Month

May is Asthma Awareness Month. Together we can help control asthma. During Asthma Awareness Month the National Asthma Education and Prevention Program (NAEPP) encourages you to discover how. Visit the NACI’s WAD Web page for more asthma related info.

Join the NHLBI's Asthma Awareness Twitter Chat with U.S. News on May 14 from 2:00-3:00 p.m. EDT. Other participants include representatives from the Office of the Surgeon General, the Centers of Disease Control and Prevention, the University of Wisconsin, and the American Thoracic Society. Follow the chat using the #AsthmaChat hashtag.

Asthma Clinical Trials

Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway for Asthma, visit www.clinicaltrials.gov.

Children and Clinical Studies Logo

Visit Children and Clinical Studies to hear experts, parents, and children talk about their experiences with clinical research.


Asthma in the News

May 18, 2014
NHLBI Media Availability: Vitamin D supplementation does not reduce asthma treatment failure in people with low Vitamin D, but some benefits suggested.
Supplementing inhaled corticosteroids (ICS) with vitamin D does not reduce the rate of treatment failure in patients with asthma and vitamin D insufficiency, finds a new NIH-funded study. The Vitamin D Add-on Therapy Enhances Corticosteroid Responsiveness in Asthma (VIDA) trial randomized 408 adults with low vitamin D and mild/moderate asthma to receive the ICS ciclesonide supplemented with either high-dose vitamin D3 or placebo.

View all Asthma Press Releases

 
June 15, 2012 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.