Allergy Testing
Mark E. Reiber, MD, FACS, FAAOA
When should I get tested?
If you have symptoms more than three months a year, despite medications and environmental control, then it’s time for allergy testing.
There are two goals: to properly direct avoidance measures and to enable immunotherapy. It isn't reasonable to cover mattresses or exile the cat if you aren't sure dust mites and pets are the problem. Each positive skin test identifies a particular allergy. If you are allergic to 10 common antigens in the area, then a mixture of these allergens is made for injections or as drops under the tongue.
How is the test done?
There are many different methods of testing and variation among doctors. Results can vary greatly depending on the type of testing performed.
At ENT Carolina, we use a combination of a prick and intra-dermal test called modified quantitative testing (MQT). It takes approximately an hour for 40 tests. Prick testing uses an 8 pronged, plastic device gently creating a small wheal in the skin of the arms. With positive reactions, no further testing is required. For negative results, a small TB needle is used to raise a skin wheal read in 10 minutes.
What am I tested for?
Our carefully selected panel includes the area’s most common weeds for the fall, grasses for the summer and fall, trees for the spring, molds, animal dander and other non-pollens for year long problems. Some antigens are so structurally similar to others, they do not have to be tested individually (cross-reactivity).
What about food allergies?
We do not do skin testing for foods for a number of reasons. In most cases, other than patients under 5 years of age, we believe food allergies are not significantly responsible for upper respiratory tract diseases. In addition, we recommend elimination and challenge diet testing as the gold standard test when necessary. Anaphylactic (shock) allergy to foods do exist such as shellfish and peanut allergies and cause life threatening swelling, and airway compromise. These should be diagnosed with blood testing (RAST) and treated with avoidance, not immunotherapy.
Can I have a blood test for allergies?
There are occasions when blood testing (RAST) for environmental allergies is recommended. We find blood testing to be less sensitive than skin testing, especially for molds, and we limit its use to only a few situations.
Can you use previous allergy test results from other doctors’ offices?
There are times when this is possible for making sublingual immunotherapy SLIT, but not injections (SCIT).
Are there medications that can affect my testing?
It is very important to inform us of all medications you are taking prior to testing. Antihistamines or medications with antihistamine like effects will block reactions giving false negatives. A class of anti-hypertensive medication, known as “beta blockers”, is specifically contraindicated for both testing and immunotherapy. They block the effectiveness of rescue medications used in the unlikely event of an anaphylactic reaction.
What can I expect after the test?
Patients will often note delayed skin reactions usually to molds. This is normal, but these reactions can be large and bothersome. Cortisone cream and an oral antihistamine can help with itching and redness.Are there any risks to allergy testing?
Risks include: itching, nasal congestion or drainage, throat tightness, cough, or breathing difficulty. These can progress to more severe, potentially life-threatening situations such as anaphylactic shock or death.
Can I be tested if I am pregnant?
Patients who are pregnant should not be allergy tested. Patients who become pregnant while on immunotherapy may continue at the current dose but may not advance on therapy until after delivery.