Allergy testing

From MEpedia, a crowd-sourced encyclopedia of ME and CFS science and history

Allergy testing encompasses a variety of tests to detect an allergic response, that is, immune system overreaction to something inhaled, ingested or touched. This may include skin, blood or challenge testing, the latter necessitating close supervising by a specialized physician, typically an allergist.[1]

Skin test[edit | edit source]

Skin testing for allergies can come in a variety of forms: a skin prick test, also called a puncture or scratch test; a skin injection test; or a patch test.[2]

Skin prick test[edit | edit source]

Skin prick testing tests for allergic reactions to as many as 40 different substances by lightly pricking the skin with the potential allergens, using a new lancet for each substance. These scratches are superficial and only briefly uncomfortable; they do not draw blood. The test compares the skin's reaction to these substances to two controls: histamine and either glycerin or saline. Histamine typically prompts a skin reaction; if it does not, the rest of the testing may produce false negatives. On the other hand, most people will not react to either glycerin or saline. If you do, this skin sensitivity make cause false positives in the rest of your testing and any positive results will be interpreted cautiously.[2]

Results take about 15 minutes and an allergic reaction indicated by a raised, red, itchy bump (wheal) at the site, which the provider performing the test will measure.[2]

Skin injection test[edit | edit source]

Patch test[edit | edit source]

Blood test[edit | edit source]

Challenge test[edit | edit source]

At-home testing[edit | edit source]

The Cleveland Clinic cautions against at-home testing, citing potential errors and misinterpretation that doctor-supervised testing can help avoid, like mistaking as an allergy what is actually an intolerance or an infection.[3] For instance, at-home tests may evaluate for immunoglobulin G (IgG) instead of immunoglobulin E (IgE), but only the latter indicates allergy.[3] Hair follicles, used by some at-home kits in lieu of blood sample, contain no IgE so cannot confirm an allergy.[3]

See also[edit | edit source]

References[edit | edit source]

  1. "Allergy Testing". American Academy of Allery Asthma & Immunology. Retrieved February 24, 2019.
  2. 2.0 2.1 2.2 "Allergy skin tests - Mayo Clinic". Mayo Clinic. Retrieved February 26, 2019.
  3. 3.0 3.1 3.2 "3 Reasons Home Allergy Tests Probably Won't Help You". Health Essentials from Cleveland Clinic. November 16, 2017. Retrieved February 26, 2019.