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The Facts

Asthma is a chronic lung condition. Inflammation, increased mucus, and muscle tightening cause the airways to narrow, and as a result, air can't move through the lungs as well as it should, which makes it difficult to breathe.

For reasons we do not completely understand, asthma is becoming more common each year, especially in children. According to the World Health Organization (WHO) and the Global Asthma Network, as many as 334 million people in the world may have asthma. Over 3 million Canadians suffer from this condition.


The cause of asthma is poorly understood, but it may be partly inherited. Everyone's lungs are sensitive to different things such as pollen, air pollution, or strong chemicals. In simple terms, people with asthma have lungs that are more sensitive than average.

There are 3 processes in the lungs that produce asthma symptoms. First, the inner linings of the airways become inflamed. They swell up, leaving less room for air to pass through. Second, the muscles around the airways can tighten, closing them further. Finally, the airways produce mucus in response to the inflammation, clogging the shrunken tubes.

Asthma is in part an allergic response. It may be triggered by some external substance that particularly irritates your lungs. These triggers are often small protein particles called allergens. Some people are sensitive to more than one trigger. Common allergens include:

  • animal dander
  • cockroach particles
  • grass, tree, and ragweed pollen
  • house dust mites
  • moulds

Other people can get an asthma attack from something they swallow rather than breathe. Examples of these triggers include:

  • ASA* and other anti-inflammatory medications
  • nuts or shrimp
  • preservatives found in some drinks or foods

While most people develop asthma as children, adults can become asthmatic by being exposed to allergens, irritants, or occupational sensitizers for a long time. People who work with the following products may be at increased risk:

  • antibiotics
  • cotton and flax
  • detergents
  • foams and paints
  • grains and cereals
  • insulation and packaging materials

Asthma attacks can also be triggered by non-allergic irritants, such as:

  • laughing hard, crying, shouting
  • smog and smoke
  • strong smells (e.g., paint fumes, perfumes, cleaning products)
  • suddenly breathing cold air
  • vigorous exercise
  • viral infections such as the common cold or the flu

Symptoms and Complications

Some children feel an itch on the back of the neck just prior to an asthma attack. Some people have some warning sign that they can learn to recognize. Warning signs include sore throat, dark circles under the eyes, feeling tired or irritable, or a change in the colour of your face.

Asthma varies in its severity. Some people experience asthma symptoms continuously, while others experience symptoms only if exposed to triggers. Regardless of the severity, typical asthma symptoms include:

  • chest tightness
  • coughing
  • shortness of breath
  • wheezing

With more severe asthma, these symptoms may occur at night.

Wheezing is the best-known asthma symptom, but not everyone with asthma wheezes. Some people only have a cough that doesn't seem to go away.

A really severe asthma attack is life-threatening. Even if some air is coming in, deadly carbon dioxide builds up in the blood. If you or a family member can't breathe and the normal medication isn't working, call 9-1-1 or your local emergency number.

Making the Diagnosis

Any one of the symptoms listed above is a good enough reason to see your doctor for a checkup. Your doctor will review your medical and family history, and he or she will ask you about your symptoms and if something seems to trigger them. Your doctor will examine your nose, listen to your lungs, and may measure your lung function with tests called pulmonary function tests. Your doctor may also suggest blood, sputum, or other tests to eliminate other possible conditions such as throat infection or cystic fibrosis.

An allergist or other doctor can identify your triggers by scratching the skin with tiny amounts of various allergens to see which ones may be triggers in your asthma.

Treatment and Prevention

There's no cure for asthma. It's a chronic condition that can last a lifetime. The goal of asthma treatment is to keep you as symptom-free as possible. This includes being able to engage in normal activities, keeping the use of rescue medications down (less than 4 doses per week), having no daytime and nighttime symptoms, and eliminating school or work absenteeism due to asthma. This goal can be reached by most people with asthma.

There are four main things you can do to manage your asthma:

  • Avoid triggers.
  • Ask your doctor for a written "asthma action plan." An asthma action plan describes how to monitor your asthma symptoms and take your asthma medications. It also explains how to tell if your asthma is getting worse and what to do if this happens.
  • If recommended by your doctor, use "preventer,” also called "controller" medications such as corticosteroids (e.g., beclomethasone*, budesonide, ciclesonide, fluticasone, or mometasone), with or without a long-acting bronchodilator (e.g., salmeterol, formoterol), leukotriene receptor antagonists (e.g., montelukast or zafirlukast), or IgE-neutralizing antibody (omalizumab).
  • Alleviate symptoms using "reliever" or "rescue" medications such as fast-acting bronchodilators (e.g., salbutamol, formoterol, or terbutaline).

Asthma triggers

Avoiding triggers is your first defence against an asthma attack. Below are some common asthma triggers and their remedies. Making simple lifestyle changes to avoid your asthma triggers can go a long way toward preventing attacks.

  • pollen (grasses, trees, weeds): Keep doors and windows closed and use air conditioning to keep pollen out.
  • dust mites (found in carpet, furniture, pillows): Use special coverings for mattresses and pillows. Remove carpets in bedrooms. Wash bedding in very hot water. Keep humidity in the room between 30% and 40%.
  • animal hair and dander: Pet removal is the best way to avoid pet allergen. If you have pets, keep them out of bedrooms and off furniture.
  • mould: Get a dehumidifier to eliminate mould. Avoid freshly cut grass.
  • environment (smoke, pollution, cold air): Stop smoking and avoid all smoky areas. Stay indoors when the outside air quality is poor. Cover your nose and mouth in cold weather.
  • exercise: Use your reliever medication 10 to 15 minutes before exercising. Warm up and cool down for 3 to 5 minutes.

Although avoiding triggers is an important part of asthma management, it is not always possible to escape them completely. Therefore, medications are often needed to prevent and treat asthma symptoms.

Asthma prevention medications

The most common asthma prevention medications are called corticosteroids (e.g., beclomethasone, budesonide, ciclesonide, fluticasone or mometasone), which are inhaled through a "puffer" or inhaler. They are designed to decrease the swelling or inflammation in your airways. It usually takes a week or two for these medications to get the swelling and inflammation under control. They don't provide fast relief of asthma symptoms, but they will help prevent future symptoms. They control inflammation, which is the underlying cause of asthma.

If corticosteroids do not control your asthma symptoms, your doctor may suggest that you use a long-acting bronchodilator (e.g., salmeterol, formoterol) combined with your corticosteroid in a single combination inhaler.

For some people, leukotriene receptor antagonists (e.g., montelukast, zafirlukast) may be used to help control asthma. These medications work by blocking a chemical from causing inflammation in the airways. If your asthma is caused by allergies and your asthma symptoms have not been controlled with corticosteroids, your doctor may suggest allergy shots or an injectable medication called omalizumab.

People with asthma symptoms often need treatment that provides immediate relief. Fast-acting bronchodilators (e.g., salbutamol, formoterol, or terbutaline) work quickly to relax the muscles around the airways and allow you to breathe more easily. These are reliever medications that treat the symptoms but not the underlying cause. If you are using relievers 4 or more times a week (not including before exercise), talk to your doctor or health care professional. You may need some changes in your medications.

Asthma itself is difficult to prevent, but a lot can be done to reduce or eliminate your asthma symptoms.

If your doctor has given you a preventive medication to use every day, follow the instructions carefully. If you use it as suggested, it should control the swelling in your airways and reduce your asthma symptoms over the long term.

Using your inhaler

Since asthma medications are often inhaled through a "puffer," they require extra knowledge and care on your part. Asthma inhalers have to be used properly to get the right amount of medication into your lungs.

Learning how to use inhalers properly can take some practice. Ask your doctor or health care professional to check to see if you are using your inhaler properly. If you are using a metered-dose inhaler (MDI), which is a pressurized inhaler, your doctor may recommend a spacer device that fits on your inhaler to make it easier for you to ensure that more of your medication is reaching your lungs. Spacers also help to reduce some of the side effects of inhaled corticosteroids. Spacer devices are not needed for dry-powdered devices that are not pressurized.

As part of your asthma treatment plan, your doctor may suggest that you use a peak flow meter. A peak flow meter helps you to monitor your lung function and it gives an indication of how well your asthma is controlled. It will also help you monitor how well your medications are working, recognize when you need to adjust your medications as recommended by your doctor or health care professional, and know when to get emergency medical attention.

Keeping a diary of your asthma symptoms is also an important way to monitor your asthma control.

*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For information on a given medication, check our Drug Information database. For more information on brand names, speak with your doctor or pharmacist.

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