Diagnostic Tests in Allergy

Abstract

Many physicians have the mistaken impression that allergic diseases are diagnosed by allergy tests. Allergic diseases can be diagnosed only from the patient’s history of symptoms and compatible physical findings. If the symptoms are typical of allergic disease and repeatedly associated with allergen exposure, a diagnosis of allergy is highly probable. A common clinical example is a patient who states that every time he or she is around cats, red, itchy eyes, sneezing, and nasal congestion develop. These typical allergic symptoms when associated with exposure to cats suggest that the patient is cat allergic. Two other important factors are the number of times the symptoms have been associated with allergen exposure and whether similar symptoms occur without allergen exposure. If the symptoms are exclusively related to cat exposure and have occurred on multiple occasions, the diagnosis is relatively certain. Finding superficial conjunctivitis, nasal congestion, and rhinitis on examination would help confirm the history. The final step for confirming a diagnosis of cat allergy would be to demonstrate that the patient has cat-specific IgE antibodies.