What is allergy?
An allergy is an unpleasant physical reaction that a person experiences when the body is exposed to a substance to which that person is hypersensitive. Such substances, which are harmless to many people, are called allergens. Allergy can affect a wide variety of organs in the body and manifests a range of symptoms.

How is allergy diagnosed?
The diagnosis of allergy begins with assessment of the patient's clinical history and symptoms. Allergy testing may then be used to identify the specific causes of the allergic reaction.

Traditionally, a patient was tested for allergy by applying a small quantity of allergen to a puncture in the skin and measuring the reaction that develops. Skin testing is qualitative and highly technique-dependent and may result in some discomfort for the patient.

Now, advanced technology is available that permits the physician to diagnose allergy from a blood sample. The test quantitatively measures immunoglobulin E (IgE) that is specific to the allergens being tested. A single blood sample can provide allergen-specific IgE test results to a variety of allergens, allowing primary care physicians the opportunity for early diagnosis and treatment of allergic patients.

Why is it important to test for allergies?
Diagnostic allergy testing can play an important role in assessing the potential of atopic disease in symptomatic patients. Accurate diagnosis of allergen sensitivity can allow health care providers to develop an optimal therapeutic approach.

Early diagnosis and treatment of the allergic patient has been shown to modify the course of the disease and prevent subsequent development of other conditions such as asthma.^1,2,3 As reported in the Expert Panel Report 2 funded by the National Institutes of Health, atopy, the genetic state of hyperresponsiveness to allergens, is the strongest identifiable predisposing factor for the development of asthma.⁴ It has been hypothesized that allergic sensitization at a young age results in a state of chronic airway inflammation, which increases the child's susceptibility to nasal and ear infections.^1,3 Chronic allergy-mediated inflammation and associated infections can cause mucosal damage and lung remodeling that can ultimately lead to asthma.

A number of studies, including one published in the 1999 World Health Organization ARIA Workshop Report, indicate that early treatment of allergy can change the course of disease progression, with clinical intervention appearing the most effective if treatments are initiated before the age of six. This finding emphasizes the importance of early diagnostic testing.^1,3

References

1. Bousquet J, van Cauwenberge P, Khaltaev N. World Health Organization. Allergic rhinitis and its impact on asthma. ARIA Workshop Report. In collaboration with the World Health Organization. December 7-9, 1999, Geneva, Switzerland. J Allergy Clin Immunol. 2001; 108(5 Suppl):S147-334.
2. Allergic factors associated with the development of asthma and the influence of cetirizine in a double-blind, randomised, placebo-controlled trial: First results of ETAC®. Pediatric Allergy Immunol. 1998; Aug; 9(3):116-124.
3. Martinez FD. Development of wheezing disorders and asthma in preschool children. Pediatrics. 2002; Feb; 109(2 Suppl):362-367.
4. National Asthma Education and Prevention Program. Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma. Bethesda, Md: US Department of Health and Human Services, National Institutes of Health; 1997. [NIH publication 97-4051].
5. Skoner DP. Complications of allergic rhinitis. J Allergy Clin Immunol. 2000; 105(6 Pt2):S605-609.