Causes and Risk Factors of Asthma

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It's impossible to pinpoint one definitive cause of asthma, as several factors—genetics, pollution, smoking, and more—are suspected to, in some combination, give way to the condition. What triggers asthma in those who have it is personal and can range from allergens like pollen and dander to non-allergic factors like exercise or having a common cold. Triggers prompt production of extra mucus and swell, challenging already sensitive, inflamed airways and making it difficult to breathe.

Knowing what causes you to have an asthma attack is an essential part of your care plan, as trigger avoidance is the most important thing you can do to live well with this condition.

Common Causes

The reason why people get asthma isn't fully established, but it's thought to be a mixture of genetic predisposition and environmental factors. According to the American Lung Association, you are at increased risk of developing asthma if you have:

  • Family history of asthma
  • Viral respiratory infection in infancy or childhood
  • Allergies
  • Occupational exposure to dust or chemical fumes
  • Smoked cigarettes, your mother smoked during pregnancy, or exposure to secondhand smoke
  • Exposure to air pollution
  • Obesity

One pattern of disease progression is seen in some people with allergic asthma. They may have eczema (atopic dermatitis) in infancy and then develop food allergies. This is followed by hay fever and their condition eventually progresses to asthma. But this is not universal.

Asthma Triggers

There are several common asthma triggers, which are substances and activities that set off asthma symptoms when you are exposed to them. What affects your asthma, and to what extent, is highly personal. The broad categories are:

  • Indoor triggers
  • Outdoor triggers
  • Foods
  • Exercise
  • Respiratory infections
  • Medications

Indoor Triggers

Americans spend as much as 90% of their lives indoors. As a consequence, indoor allergens can play a significant role in worsening asthma.

Identifying the indoor allergens affecting your asthma could lead to significant improvements by either prompting you to avoid the triggers or develop a plan (with the help of your healthcare provider) to deal with them.

Indoor asthma triggers that may affect you include:

  • Secondhand smoke: Secondhand smoke, or environmental tobacco smoke, consists of a mixture of both the smoke irritants exhaled by smokers of cigarettes, pipes, or cigars and from the burning tobacco itself. Environmental tobacco smoke contains more than 250 different cancer-causing chemicals such as benzene, vinyl chloride, and arsenic that may irritate your airways and lead to asthma symptoms.
  • Dust mites: Dust mites are small arthropods in every home that cannot be seen with the naked eye. They feed on tiny flakes of skin found on bedding products (mattresses, pillows, bed covers), carpets, upholstered furniture (or anything covered in fabric), and stuffed toys. Dust mites can both trigger asthma symptoms or lead to them in people without a previous history of asthma.
  • Mold: Molds can grow anywhere moisture is present. They commonly grow on wet or damp surfaces in locations like bathrooms, kitchens, and basements. If molds are a problem in your home, controlling moisture may lead to better control of your asthma.
  • Cockroaches and other pests: Body parts, urine, and droppings of cockroaches and pests contain specific proteins that can trigger allergy symptoms. It is essential to remove hiding places for pests and keep countertops and other exposed areas free from food and water.
  • Pets: Allergens from your pets' dead skin, droppings, urine, and saliva can trigger asthma. If you have pets, try to have a pet-free area, such as the bedroom, and to clean your house frequently, especially rugs, upholstered furniture, and stuffed toys. If you're thinking of welcome a pet into your home, you might reconsider knowing how they can affect asthma symptoms.
  • Nitrogen dioxide: Nitrogen dioxide is a gas that comes from gas stoves, fireplaces, and gas space heaters that can irritate the lungs and lead to shortness of breath.

Outdoor Triggers

During the spring and fall, airborne pollens and molds commonly trigger asthma symptoms. These include:

  • Pollens: Pollens are small, powdery granules that are essential for plant fertilization. Weather conditions greatly influence the amount of pollen in the air. Pollen season will vary depending on where you live, but generally lasts from February to October. Pollens from many different kinds of grasses, weeds, and trees may trigger allergy symptoms.
  • Molds: There are many molds in the outdoor environment that become airborne, but unlike pollens, do not have a particular season. Many outdoor molds can be found in soil and outdoor vegetation.
  • Weather: You may notice that the weather significantly affects your asthma symptoms. On days that are hot, dry, and windy, pollen counts will likely be higher, and you may experience more asthma symptoms. Rain may also lead to increased molds that may worsen symptoms. On the other hand, days that are cloudy with very little wind may result in only minimal asthma symptoms. Because you cannot avoid weather like allergens, you must have effective treatment for your asthma.

Respiratory Infections

The common cold, influenza, and other respiratory infections may trigger your asthma. While you cannot always prevent a cold, you can do your best and try: Make sure you wash your hands frequently, avoid touching your nose or mouth while in public or when around someone with a cold, and get appropriate immunizations.

Less Common Asthma Triggers

Though these triggers are less common, they are no less important.

  • Medications: A number of different medications may trigger your asthma. If you believe any medication is worsening your asthma, talk with your doctor about whether or not changing your dose or your drug regimen all together is advised. Some of the most common offenders are pain medications (aspirin, ibuprofen, naproxen) and beta blockers.
  • Certain foods: Certain food allergies (fish, soy, egg, wheat, tree nuts, and others) may also trigger your asthma. These reactions are more common in infants and children. Your doctor may ask you to keep a food diary to help determine if specific foods are worsening your (or your child's) asthma, or allergy testing may be needed to help get a diagnosis.
  • Exercise: If you notice symptoms like wheezing or coughing while exercising, you may have exercise-induced bronchoconstriction, commonly referred to as exercise-induced asthma. About 5% of the U.S. population has exercise-induced asthma and will benefit from getting a diagnosis and the appropriate treatment.


Because asthma runs in families, genetics must be one of the underlying risk factors. Over 100 different genes have been associated with allergic asthma , but they seem to bring only increased risk rather than clearly causing the condition. These genes are usually involved in your immune reactions and lung functions.

It may take an environmental exposure to trigger the epigenetic changes to the DNA that then produce the allergic reaction. As a result, allergic asthma may be seen being passed down through generations, though not all family members who carry the gene develop asthma.

The American Lung Association notes that you are three to six times more likely to have asthma if you have a parent who has asthma.

Lifestyle Risk Factors

Smoking and exposure to secondhand smoke are common asthma triggers. If you smoke, quitting is the best course of action. This will also lessen the risk to those in your household.

Obesity is not only a risk factor for developing asthma, but people with asthma who are obese often have worse symptoms and control of their condition.

Avoiding your asthma triggers is part of controlling your asthma. Whether you are the person with asthma or you are caring for a child with asthma, you need to do some detective work to determine the triggers. Asking yourself the following questions may help:

  • Do the symptoms occur primarily at home or at work? This may indicate that there is an environmental component you need to find, like molds, dusts, or odors.
  • Do the symptoms fluctuate with the season? This may indicate a more allergic condition, such as allergic rhinitis or hay fever.

While identifying the triggers may not always be easy, doing so will help you breathe easier.

A Word From Verywell

If you can avoid asthma triggers, you can avoid a lot of problems that can come with your disease. Addressing asthma is a marathon. There is no cure, but the condition can be managed and symptoms placed under control will commitment to treatment and avoidance for the long term.

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