The terms allergies and asthma often are linked together. In reality, they are two different medical conditions although the cause of both conditions is closely related. Some children have allergies without asthma, and some have asthma without allergies, but most children have both. The medical community, though, is taking closer looks at how treatment of allergies can impact the management of asthma symptoms.
Asthma symptoms occur when inflamed airways overreact to a variety of stimuli including physical activity, upper respiratory viral infections, allergens (such as pollen or molds), and irritants (such as tobacco smoke). Exposure to these stimuli — often called triggers — can create more swelling and blocking of the airways. (Also see Chapter 4.)
On the other hand, allergies are diseases of the immune system that cause an overreaction to allergens. Allergies generally are grouped together by the kind of trigger, time of year they occur, or where symptoms appear on the body. Allergens can be inhaled into the lungs, ingested by mouth, injected through needles (medications) or insect stings, or absorbed through skin.
Not all children with allergies will develop asthma. However, approximately 80 percent of children with asthma also have allergic asthma, a type of asthma caused by allergens. This makes allergens the most common asthma trigger.
The connection between allergies and asthma, though, is gaining more attention — especially in light of the fact that treatment of underlying allergies has been found to often improve asthma symptoms.
Signs of Asthma and Allergies
While every child is different, you may detect a few distinct signs along the way that might indicate asthma. While a health care provider can suggest tests to help diagnose asthma, a few clues might be right in front of you to indicate that your child might have more than just allergies.
For example, the lowly, microscopic dust mite — one of the most common asthma triggers in homes — is found everywhere. Dust mites create their homes in upholstery, carpeting, and bedding, and their remains often make up a substantial amount of dust found indoors.
A child with a dust mite allergy may show signs and symptoms similar to hay fever. These allergic symptoms can include sneezing, runny nose, itchy and watery eyes, nasal congestion, itchy nose, swollen mouth or throat, swollen or bluish-tinted skin under the eyes, postnasal drip, cough, irritability, or facial pain or pressure.
But the child with asthma also may show signs and symptoms such as lung congestion, wheezing, and shortness of breath. She may be more likely to have these symptoms at night while in a bed filled with dust mites.
A dust mite allergy can range from mild to severe. With a mild case of asthma, a dust mite allergy might consist of an occasional runny nose, watery eyes, and sneezing. For severe cases, the child might have symptoms such as persistent wheezing, sneezing, facial pressure, and congestion.
During a process called sensitization, your child's immune system could mistakenly identify an inhaled dust mite residue as an invader. His body then produces an antibody against it called immunoglobulin E (IgE). These antibodies often are the prime culprits in children who develop asthma after the age of three.
Then, the next time he's exposed to the dust mite residue, his immune system begins an allergic reaction. The IgE antibodies will trigger the release of histamine, an inflammatory chemical that causes swelling of the mucous membranes in his lungs, nose, sinuses, and eyes. This results in wheezing, runny nose, sneezing, watery eyes, and increased mucus production.
Since IgE is involved in the early stages of a body's response to an allergen, ongoing research has emphasized that reducing IgE may help prevent asthma symptoms and attacks before they even begin. A child's IgE level can be determined by a blood test.
Since many children with asthma have allergies, consider checking with your health care provider to see if an allergy evaluation will be part of her treatment.
Ongoing research has found that allergy testing can help a health care provider tailor a child's allergy and asthma care. This should be accompanied by individual instruction that provides children and parents with information that assists them in identifying — and removing — allergens or triggers that could cause problems.
The use of allergy testing — whether done through either a blood test or a skin test (performed by an allergy specialist) — is still often overlooked by many health care providers. With the blood test, a blood sample is collected to test for specific antibodies for allergens (such as IgE). With skin testing, small amounts of allergens are applied to the skin, and any local reactions are observed. For the earlier example of dust mites, you would develop a temporary red, itchy bump where the dust mite extract is scratched onto the skin.
In particular, many of those providing care to children with asthma in the past under the age of five years have not used the tests — citing too many false positives. However, more evidence is emerging that testing could be valuable in treating these patients.
In one study, allergies often were found to be underdiagnosed in a study of more than 5,000 children living in urban settings. Less than half of the children had received allergy diagnoses, and only 40 percent of those children had received allergy testing. Those who had undergone testing were more likely to be taking allergy medication (in addition to their asthma medication) and to be exposed to fewer environmental triggers in the home.
Researchers noted the strong overlap between the management of allergies and better asthma outcomes in terms of such factors as fewer days missed from school.
If your child's symptoms are difficult to control or are producing bothersome nose, eye, or asthma symptoms, your health care provider may suggest allergy shots (immunotherapy) to desensitize her to dust mites.
In immunotherapy, your child would receive injections, for instance, of dust mite extract (if she was allergic to dust mites). The doses would be increased once or twice a week. Once a maintenance dose has been reached, injections would be needed every four weeks.
Allergy testing can be helpful in identifying what your child may be allergic to. However, it will not be helpful in identifying if your child has asthma.
Rhinitis and Asthma
One particular allergy that has attracted attention for its reported tie to asthma is allergic rhinitis, which is better known as hay fever. For years, both have been treated as separate medical conditions. Allergic rhinitis can be caused by outdoor allergens (pollens, molds) and indoor allergens (animal dander, indoor molds, dust mites).
The treatment of allergic rhinitis includes use of antihistamines, decongestants, and anti-inflammatory nose sprays that are similar to medications used for asthma patients.
An estimated 10 to 20 percent of young school children and 15 to 30 percent of teenagers worldwide have rhinitis. This condition usually starts at three to five years of age, but it is commonly found years later in childhood and adolescence, when severe forms could be more frequent.
Ongoing research has cited evidence that allergic rhinitis and asthma are linked — suggesting the idea of “one airway, one disease.” This means that management of one disease was found to improve when the other condition was taken into account.
One recent study found that one in three allergic rhinitis patients may go on to develop asthma within ten years — further increasing the number of children with asthma.