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Medical Author:

Girish Sharma, MD

Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Causes of Asthma

Asthma in children usually has many causes, or triggers. These triggers may change as a child ages. A child's reaction to a trigger may also change with treatment. Viral infections can increase the likelihood of an asthma attack. Common triggers of asthma include the following:

• Respiratory infections: These are usually viral infections. In some patients, other infections with fungi, bacteria, or parasites might be responsible.



• Allergens (see below for more information): An allergen is anything in a child's environment that causes an allergic reaction. Allergens can be foods, pet dander, molds, fungi, roach allergens, or dust mites. Allergens can also be seasonal outdoor allergens (for example, mold spores, pollens, grass, trees).



• Irritants: When an irritating substance is inhaled, it can cause an asthmatic response. Tobacco smoke, cold air, chemicals, perfumes, paint odors, hair sprays, and air pollutants are irritants that can cause inflammation in the lungs and result in asthma symptoms.



• Weather changes: Asthma attacks can be related to changes in the weather or the quality of the air. Weather factors such as humidity and temperature can affect how many allergens and irritants are being carried in the air and inhaled by your child. Some patients have asthmatic symptoms whenever they are exposed to cold air.



• Exercise (see below for more information): In some patients, exercise can trigger asthma. Exactly how exercise triggers asthma is unclear, but it may have to do with heat and water loss and temperature changes as a child heats up during exercise and cools down after exercise.



• Emotional factors: Some children can have asthma attacks that are caused or made worse by emotional upsets.



• Gastroesophageal reflux disease (GERD): GERD is characterized by the symptom of heartburn. GERD is related to asthma because the presence of small amounts of stomach acid that pass from the stomach through the food pipe (esophagus) into the lungs can irritate the airways. In severe cases of GERD, there may be spillage of small amounts of stomach acid into the airways initiating asthmatic symptoms.



• Inflammation of the upper airways (including the nasal passages and the sinuses): Inflammation in the upper airways, which can be caused by allergies, sinus infections, or lung (respiratory) infections, must be treated before asthmatic symptoms can be completely controlled.



• Nocturnal asthma: Nighttime asthma is probably caused by multiple factors. Some factors may be related to how breathing changes during sleep, exposure to allergens during and before sleep, or body position during sleep. Furthermore, as a part of biological clock (circadian rhythm), there is reduction in the levels of cortisone produced naturally within the body. This may be a contributing factor for nighttime asthma.



• Recent reports of possible association between asthma and acetaminophen use may be due to the fact that children with severe asthma may be more likely to be take acetaminophen for viral or other infections that may actually be due to asthma or may precede an asthma diagnosis.

Allergy-related asthma

Although an estimated 75%-85% of people with asthma have some type of allergy, the allergy isn't always the primary cause of asthma. Even if allergies are not your child's primary triggers for asthma (asthma may be triggered by colds, the flu, or exercise for example), allergies can still make symptoms worse.

Children inherit the tendency to have allergies from their parents. People with allergies make too much "allergic antibody," which is called immunoglobulin E (IgE). The IgE antibody recognizes small quantities of allergens and causes allergic reactions to these usually harmless particles. Allergic reactions occur when IgE antibody triggers certain cells (called mast cells) to release a substance called histamine. Histamine occurs in the body naturally, but it is released inappropriately and at too high an amount in people with allergies. The released histamine is what causes the sneezing, runny nose, and watery eyes associated with some allergies. In a child with asthma, histamine can also trigger asthma symptoms and flares.

An allergist can usually identify any allergies a child may have. Once identified, the best treatment is to avoid exposure to allergens whenever possible. When avoidance isn't possible, antihistamine medications may be prescribed to block the release of histamine in the body and stop allergy symptoms. Nasal steroids can be prescribed to block allergic inflammation in the nose. In some cases, an allergist can prescribe immunotherapy, which is a series of allergy shots that gradually make the body unresponsive to specific allergens.

Exercise-induced asthma

Children who have exercise-induced asthma develop asthma symptoms after vigorous activity, such as running, swimming, or biking. For some children, exercise is the only thing that triggers asthma; for other children, exercise as well as other factors trigger symptoms. Young children with exercise-induced asthma may have subtle symptoms such as coughing or undue breathlessness after physical activity during play. Not every type or intensity of exercise causes symptoms in children with exercise-induced asthma. With the right medicine, most children with exercise-induced asthma can play sports like any other child. In fact, over 10% of Olympic athletes have exercise-induced asthma they've learned to control.

If exercise is a child's only asthma trigger, the doctor may prescribe a medication that the child takes before exercising to prevent airways from tightening up. Of course, asthma flares can still occur. Parents (or older children) must carry the proper "rescue" medication (such as inhalers) to all games and activities, and the child's school nurse, coaches, scout leaders, and teachers must be informed of the child's asthma. Make sure the child will be able to take the medication at school as needed.

cromolyn or nedocromil, long-acting bronchodilators, theophylline, and leukotriene antagonists. The other category is medications that provide instant relief from symptoms (rescue medications). These include short-acting bronchodilators and systemic corticosteroids. Inhaled ipratropium may be used in addition to inhaled bronchodilators following asthma attacks or when asthma worsens.