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How Are Allergy Tests Done And What Will They Tell Us?

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My toddler was recently diagnosed with asthma. His doctor recommended allergy testing. How is the testing done? What will the results tell us?

Allergy tests can give very useful information about what your allergies are. They help to show which allergens are causing the symptoms. This testing is generally safe and effective for adults and children of all ages. The allergist will pick the best test for the patient. This is based on the clinical history, physical examination, and potential allergy triggers. The results of this testing will help the allergist make a treatment plan to reduce or eliminate potential allergens. It will include specific information to help manage the allergy symptoms.

Skin testing is the most common type of test used. It is relatively painless. A very small amount of the allergen (e.g., allergen extract) is placed on your skin. This area is pricked or scratched. If the patient has an allergy, there may be a little swelling at the site of the prick test. It will look and feel like a mosquito bite. This happens where the allergens they are allergic to were placed. There is not a long wait to see what is triggering the allergies. Reactions happen within 15-20 minutes. Patients generally won’t have any other symptoms, besides the small hives where the tests were done. These go away within 30 minutes. Skin tests are best performed in an allergist’s office by an expert. This is so they can be properly placed and interpreted. Also, if any side effects happen, they can be treated immediately and appropriately.

If the results of prick skin tests are negative (no local reaction), but the physician thinks the patient might have allergies, other testing may be done. This includes intradermal skin testing, and blood testing.

  • Intradermal testing is when a small amount of allergen is applied under the skin with a syringe and needle. Intradermal tests are more sensitive than prick tests. They may be used when prick test results are inconclusive. This is mainly used for environmental allergens (e.g., pollen, animal dander), but not for food allergens.
  • Blood tests involve drawing blood, which can identify allergic antibodies (e.g., IgE) to specific allergens. The results are not available as quickly as with skin tests. It can be more expensive. IgE blood tests are generally used when skin tests might be unsafe or won’t work for the patient. This includes if they are taking certain medications (e.g., antihistamines) or have a skin condition such as atopic dermatitis or eczema that may affect the testing.

For food allergies, there are oral food challenge tests. A very small amount of an allergen is eaten. The amount is slowly increased. These challenges must be done in a medical clinic and supervised by a trained health professional.

Lastly, there are methods of allergy testing that are not useful and ineffective. These may lead to inappropriate diagnosis and treatment. They include:

  • Allergy screening tests done in supermarkets or drug stores
  • Home testing kits
  • Applied kinesiology (allergy testing by testing muscle strength or weakness)
  • Cytotoxicity testing for food allergy
  • Rinkel skin titration method
  • Provocative neutralization testing
  • Immunoglobulin G (IgG) testing for food allergy
  • Sublingual provocation
Allergy, Diagnosis
Answered by

John M. James, MD, is a board-certified allergist. He is also President of Food Allergy Consulting and Education Services, LLC. He has worked as a medical specialist in the field of allergy, asthma, and immunology for over 30 years. Dr. James received his bachelor’s degree from the University of Arkansas and his Doctor of Medicine degree from the University of Tennessee. He is board certified by the American Board of Allergy and Immunology.

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