What is asthma?

Asthma is a chronic disease of the air passages in the lungs. The actual cause of asthma is not known. Asthma experts believe that a combination of genetic and environmental factors can cause asthma or at least increase sensitivity to asthma triggers. These factors include:

  • family history
  • childhood viral infections
  • early allergen exposure
  • living in urban settings

Allergies often are associated with asthma. But not all people with allergies suffer from asthma.

Doctors have identified the two main conditions that cause asthma symptoms: inflammation and airway constriction.


With asthma, the inside walls of the airways are swollen, or inflamed. This inflammation makes the air passages particularly sensitive to irritants and asthma triggers. The swelling narrows the air passages, making it difficult for air to pass through the airways. This makes it hard to breathe normally.

Airway constriction

When the airways come into contact with certain asthma triggers, the muscles around the airways tighten. This causes the air passages to become even narrower. It also causes you to have a tight feeling in the chest. Some say it feels like a rope is being tightened around your chest. Mucus can get lodged in the narrowed airways, causing more trouble with breathing.

The triggers that cause the inflammation and airway constriction can vary from patient to patient. Understanding your triggers is essential to managing asthma.

Common asthma triggers include:

  • pollen
  • dust mites and cockroaches
  • mold
  • pet hair and dander
  • changes in weather, especially cold air
  • respiratory infections, such as the common cold
  • smoke
  • stress and strong emotions
  • physical activity
  • allergic reaction to food or sulfites
  • food preservatives
  • heartburn/acid reflux
  • certain medications, such as aspirin or beta blockers

Work with your doctor to help figure out your triggers, and then come up with strategies to avoid them.

There are a number of factors thought to increase the risks of developing asthma. They include the following.

Family history

If one of your parents has asthma, then you have a greater risk of developing it.

Gender and age

Asthma is more common in children than adults. Boys are more likely to develop asthma than girls. Risks are equal for men and women for adult-onset asthma.


Sensitivity to allergens is often an accurate predictor of your potential to develop asthma. These allergens often include:

  • dust
  • pet dander
  • mold
  • toxic chemicals

Allergens can trigger asthma attacks after you develop asthma.


Cigarette smoke irritates the airways. Smokers have a high risk of asthma. Those whose mothers smoked during pregnancy or who were exposed to secondhand smoke are also more likely to have asthma.

Air pollution

This is the main component of smog, or ozone. Constant exposure to air pollution raises the risk for asthma. Those who grew up or live in urban areas have a higher risk for asthma.


Children and adults who are overweight or obese are at a greater risk of asthma. Although the reasons are unclear, some experts point to low-grade inflammation in the body that occurs with extra weight.

Viral respiratory infections

Respiratory problems during infancy and childhood can cause wheezing. Some children who experience viral respiratory infections go on to have chronic asthma.

Asthma is a chronic disease of the air passages in the lungs. Its cause isn’t known. Experts believe it stems from a combination of genetic and environmental factors. Triggers cause the inflammation and airway constriction that characterize asthma. Understanding your triggers is essential to managing asthma.