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Allergy Testing Services
There are several available allergy testing methods to confirm allergic sensitivities to inhaled substances (e.g., pollens, dust mites, molds, animal dander), foods, stinging insects, medications, and contact substances. Above all, the key concept in the proper diagnosis of an allergic condition is that the patient’s history of allergic reactions is the most important diagnostic tool. Allergy testing merely serves to confirm or exclude a diagnosis of allergic sensitivity and does not alone conclusively diagnose an allergic condition. In other words, it is possible to have a positive allergy test but no allergic symptoms.
Q: What is the best allergy testing method to evaluate my allergic problem?
A: Selecting the best allergy testing method depends on many factors, including the allergic problem being evaluated, the patient’s medications, other health conditions, and personal preferences.
Allergy Testing Methods
Allergy Skin Prick Testing
This method provides a fast, safe and reliable means for identifying allergic sensitivities to inhalant allergens (e.g., pollens, dust mites, molds, animal dander), foods, stinging insects and penicillin. This procedure, which involves introduction of allergen extracts into the superficial layer of the skin via a MultiTest™ applicator device. The allergy skin test is very well tolerated by most patients of all ages. Localized wheal responses (bumps similar to mosquito bite reactions) are measured 20 minutes after the tests are applied to the skin. The itch of positive reactions is definitely worse than the “ouch” of the test, but itching typically stops within 30 minutes after the testing is completed.
- Results are available in 30 minutes.
- Negative skin prick tests for foods carry the highest degree of confidence in excluding potential culprits for allergic reactions.
- Skin prick testing is the most sensitive method for determining allergic sensitivities to inhalant allergens, stinging insects and penicillin.
- Antihistamines and certain other medications must be discontinued for several days before the testing procedure (see Allergy Skin Testing Instructions). Most people, however, can control their symptoms with nasal sprays and decongestant to allow for testing.
- Skin testing may not be possible with certain skin conditions (e.g., chronic hives or chronic eczema).
Serum IgE Allergy Testing
This method is an acceptable alternative to allergy skin prick testing for patients who have certain skin conditions or who take certain medications that would interfere with allergy skin prick testing. A laboratory requisition for IgE allergy testing for inhalant allergens or specific foods is provided for the patient’s blood to be drawn at the commercial lab of his choice.
- Antihistamines do not interfere with serum IgE measurements and thus do not need to be discontinued in preparation for this testing.
- Tracking changes in serum IgE levels for certain specific foods (e.g., milk, egg, peanut, fish) helps predict whether or not that food allergy is likely to resolve over time.
- Less sensitive than skin prick testing in detecting allergic sensitivity to inhalants, foods, stinging insects, and penicillin.
- Available IgE panels for inhalant allergens are not as robust as skin testing panels.
- A separate trip to a commercial lab is required for blood to be drawn.
- Results may take up to 10 business days to return.
Oral Food Challenges
This method is the gold standard of food allergy testing. Oral food challenges are used to determine whether or not a patient is truly allergic to a food when the history and allergy testing results are inconclusive. Oral food challenges are especially useful to prove that a child has lost allergic sensitivity to a previously problematic food. This procedure, which usually takes 4 hours, involves eating increasing doses of the food in question under close observation in our Medical City Dallas office. The challenge ends either when the patient exhibits any signs of an allergic reaction (which is promptly and aggressively treated in our office) or has no reaction with a full serving of the food. Passing a graded food challenge allows the patient to eat as much of the food as desired without any special precautions.
- The only test that can definitively prove or disprove allergic sensitivity to a food.
- A failed challenge provides an excellent opportunity to observe and treat an allergic reaction in a controlled setting with the guidance of nurses and physicians experienced in managing such reactions.
- Time consuming procedure (but we believe well worth the effort).
- Procedure involves a risk of experiencing an anaphylactic reaction. In the controlled setting of our office, allergic reactions are recognized and treated promptly and aggressively to reduce the risk of progression to a more serious reaction.
Patch testing is used to evaluate suspected reactions to a variety of substances that have been implicated in allergic contact dermatitis and other chronic allergic inflammatory conditions. This procedure involves test substances in adhesive patches applied to the back, then returning to our office to have the patches removed and test sites examined 48 hours later, then returning the next day for the test site reactions to be measured and recorded.
- It is the preferred testing method for identifying sensitivities to a variety of common substances that may be responsible for allergic contact dermatitis.
- Patch testing can also be modified to evaluate for food sensitivities associated with a condition called Eosinophilic Esophagitis.
- Time consuming, involving 3 office visits in one week.
- No showers or vigorous exercise for 48 hours after patches are placed.