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) may make your airways more reactive to substances in the air.
Some factors may be more likely to cause asthma in some people than in others. Researchers continue to explore what causes asthma.
The "Hygiene Hypothesis"
One theory researchers have for what causes asthma is 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.
What Causes Asthma Symptoms To Occur?
Many things can trigger or worsen asthma symptoms. Your doctor will help you find out which things (sometimes called triggers) may cause your asthma to flare up if you come in contact with them. Triggers may include:
Allergens from dust, animal fur, cockroaches, mold, and pollens from trees, grasses, and flowers
Irritants such as cigarette smoke, air pollution, chemicals or dust in the workplace, compounds in home décor products, and sprays (such as hairspray)
Medicines such as aspirin or other nonsteroidal anti-inflammatory drugs and nonselective beta-blockers
Sulfites in foods and drinks
Viral upper respiratory infections, such as colds
Physical activity, including exercise
Other health conditions can make asthma harder to manage. Examples of these conditions include a runny nose, sinus infections, reflux disease, psychological stress, and sleep apnea. These conditions need treatment as part of an overall asthma care plan.
Asthma is different for each person. Some of the triggers listed above may not affect you. Other triggers that do affect you may not be on the list. Talk with your doctor about the things that seem to make your asthma worse.
What Are the Signs and Symptoms of Asthma?
Common signs and symptoms of asthma include:
Coughing. Coughing from asthma often is worse at night or early in the morning, making it hard to sleep.
Wheezing. Wheezing is a whistling or squeaky sound that occurs when you breathe.
Chest tightness. This may feel like something is squeezing or sitting on your chest.
Shortness of breath. Some people who have asthma say they can't catch their breath or they feel out of breath. You may feel like you can't get air out of your lungs.
Not all people who have asthma have these symptoms. Likewise, having these symptoms doesn't always mean that you have asthma. The best way to diagnose asthma for certain is to use a lung function test, a medical history (including type and frequency of symptoms), and a physical exam.