How can I find out whether or not I have allergies? If I do have allergies in addition to my asthma, what types of treatment are available?
A strong link between asthma and allergy has been recognized for a long time and both diagnoses frequently co-exist, as explained in Question 9. Many people believe that they may be allergic to certain foods or aeroallergens, such as pollens or dog dander, for example. An astute observer might notice that after exposure to the suspected agent, an allergic symptom, such as itchy, watery eyes, nasal stuffiness, or throat tingling develops.
At the other extreme, a person might be allergic and not make the connection, not recognizing the allergy symptoms for what they are. Sometimes, the treating physician may come to suspect that a recurrent group of symptoms outside of the lungs or that persistent asthma reflects an underlying allergy. In each circumstance, consultation with an allergy specialist or allergist can be extremely helpful and is highly recommended in order to determine whether an allergy is present or not. Persons, especially children, whose asthma is persistent (as per the NAEPP’s 2007 classification) should be evaluated for the possibility of allergen-induced asthma.
The most important allergens from an asthma perspective are inhaled allergens, including indoor allergens (such as dust mites, animal dander, and cockroaches) and outdoor fungal spores. Seasonal asthma has been linked with exposure to grass, ragweed, and pollen in sensitized persons. Food allergy does not typically precipitate asthma symptoms. If your treating physician believes that you have significant symptoms of allergy, referral to an allergy specialist may be considered. Allergists are experts in evaluating and caring for children and adults who have allergic dis-eases. Evaluation always begins with a detailed history of the patient’s symptoms and a review of the family history.
The physical examination places particular emphasis on the skin, upper respiratory tract, and lungs. Important clues to diagnosing allergy often are found on close inspection of the skin, eyes, throat, and nasal passages, and on auscultation of the lungs. An attentive physician can therefore detect various specific findings of allergy if they are present on the physical examination. After obtaining a complete history and performing a physical examination, the next step in the evaluation may require specific allergy testing. Testing is performed either directly on the skin (in vivo allergy testing) or as a laboratory procedure (in vitro allergy testing) with a blood sample.
Direct testing refers to one of two techniques, some-times collectively called skin testing. The first uses the prick puncture method and is performed on the skin of the patient’s forearm or back. The prick puncture form of testing thus does not involve receiving an injection. If the result of the prick puncture test is not definitive, then the next step in the evaluation of suspected allergy may require intradermal tests, typically on the upper arm. An intradermal test requires a very superficial injection directly into the skin layer.
Indirect testing (in vitro) requires venipuncture, during which a sample (tube) of blood from a vein is obtained through a needle stick. The first commercially introduced in vitro allergy test, developed by Pharmacia Diagnostics of Uppsala Sweden, was named RAST (which stands for RadioAllergoSorbent Test) and became widely avail-able by the mid-1970s. The company developed a more refined test in 1989 called ImmunoCAP, which has now supplanted the first-generation RAST. A “positive allergy” test result reflects prior exposure followed by sensitization to the specific allergen tested. The positive test result indicates that the immune system has been stimulated to produce a protein, namely an IgE antibody specifically directed against the tested allergen.
Consider for example a college student who each year when he moves into his dorm at school in the late summer, notices several weeks of nasal congestion, cough, and a flare of his typical asthma symptoms requiring a step up in asthma medication. His allergist suspects a ragweed allergy. Direct testing with ragweed extract is positive, which means that our college student’s immune system has over time been stimulated to produce an IgE antibody (see the next question for more information on IgE) directed against ragweed. Our student sensitized to rag-weed is now “primed” to have an allergic reaction when again exposed to ragweed. When he returns to college during ragweed season, he experiences nasal symptoms and his asthma flares as a consequence of his ragweed allergy. Many mistakenly believe that blood testing (RAST or ImmunoCAP) is somehow more accurate than direct allergy testing in evaluation of allergy.
RAST is a valid technique for determining allergic sensitivity and the presence of IgE antibodies. The ImmunoCAP provides additional detailed measurement of IgE antibody levels. Specific clinical situations may lead an allergist to rec-ommend an in vitro (blood) method of testing rather than in vivo, recognizing, too, that in vivo (skin testing) requires specific skill and experience to perform. Per-sons with active skin conditions, such as eczema or psoriasis, or very reactive skin are not appropriate candidates for direct allergy (skin) testing and are better evaluated with a blood test, for instance. A very young child and anyone who has an exaggerated fear of needles would be possible candidates for RAST testing as well.
Finally, a person who requires daily antihistamine medication that cannot be temporarily discontinued should be considered for blood testing, since allowing direct (in vivo) skin testing yields unreliable results if a person is taking antihistamine medication at the time of testing. Testing for many different suspected food allergies in a young child can be performed effectively all at once with the RAST or ImmunoCAP blood test. Once the diagnosis of a specific allergy (or allergies) is established, the next step is initiating appropriate treatment. There are three basic and complementary approaches to the treatment of allergic diseases: allergen avoidance, medication, and immunotherapy.
The first measure is to avoid contact with and exposure to the allergen whenever possible. Some allergens, such as foods, can generally be passed up by careful menu planning and close review of food labels, while others, like tree pollen, cannot reason-ably be entirely avoided, and some (like an adored family pet) might be extremely difficult to stay away from. Even so, it is also important for a person with allergy to have as normal and healthy a lifestyle as possible.
If you are allergic to an environmental allergen (such as a cat, dog, or hamster) and you consistently and reliably implement successful environmental allergen control, you may not require any medication or further treatment. Environmental control alone is not however always sufficient in treating significant allergy. Despite excellent environmental control and determined efforts at allergen avoidance, additional measures are usually required for optimal allergy treatment. The second strategy in allergy treatment is the prescription of appropriate medications (pharmacotherapy) to effectively control symptoms. Note, however, that the medications prescribed for control of allergy symptoms cannot cure the underlying allergy.
Immunotherapy, commonly referred to as “allergy shots,” is the third approach employed for the treatment of allergic asthma and is the only method of treatment that has the potential to “turn down,” or possibly turn off, the ability of the immune system to react to specific allergens. If there is no allergic reaction, there will be no asthma symptoms. Consider, for instance, a patient with documented tree and grass pollen allergies whose parents came to an allergist seeking a second opinion when he was 11 years old. He had first developed allergy symptoms in first grade. Over the next 4 years, and despite excellent compliance with antihistamine pills, nasal allergy sprays, and environmental controls such as use of air conditioning and air filters, this youngster experienced worsening allergic symptoms every spring and summer. Immediately before he was brought in for his consultation, he required several courses of oral corticosteroid medication over the course of a single spring and summer season. One of our treatment recommendations included consideration of immunotherapy directed against tree and grass allergens.
This patient proceeded with immunotherapy and is now an active, sports-loving 16-year-old who no longer needs to use nasal steroid sprays and daily antihistamines in order to function. During the allergy season— spring into early summer—he takes only an infrequent antihistamine to control his markedly reduced symptoms. Participation in his favorite sports—soccer and baseball—no longer presents the challenges it did before he started his allergy treatments. Immunotherapy directed against tree and grass pollens has caused his immune system to turn down and almost turn off his ability to react allergically to either of these pollen classes. With continued therapy, it would not be unreasonable for this young man to be rid of his allergic sensitivity to the spring-season pollens.
Allergists are physicians who are experts in administering immunotherapy. Immunotherapy has been proven effective in the treatment of selected persons with allergic asthma, allergic rhinitis, and insect sting allergy. Treatment initially requires weekly visits and lasts for an average of 3–5 years but sometimes more. Over time, the interval between injection visits extends to 3–4 weeks during the maintenance phase. The 2007 NAEPP’s EPR-3 advises that immunotherapy be considered for any person with persistent asthma “if evidence is clear of a relation-ship between symptoms and exposure to an allergen to which the patient is sensitive.”
Kerrin’s comment:
We had my son tested for allergies when he was 2 years old. We were especially concerned about a peanut allergy because he had a reaction to a cookie someone brought from a bakery that we suspected had either been made with peanut oil or had come in contact with peanut ingredients. The allergy specialist performed a test on his back because he was too young to be certain he would not wipe off the serum. The hardest part was keeping him still for the 20 minutes it took for the test to complete. But they had a VCR in the office and he quickly settled down. And the test showed that he had a severe peanut allergy, so the very short discomfort was a small price to pay for knowing this potentially life-saving piece of information.