Photograph of chinchilla hair  © Daniel Friedman Review of types of Human Allergy Tests for Exposure or Sensitivity to Mold or Pet Allergens
     


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Animal & mold allergy tests: this article describes human testing for allergic sensitivity to animal, food, mold, insect, trees, grasses, and other possible environmental allergens and irritants. People who have tested as sensitive to allergens, others who have tested as "not sensitive" but who have building related complaints, and others often ask us how to test a building or home for mold, or for cat, dog, or other animal allergens. At ALLERGY TEST ACCURACY we discuss the accuracy and limitations of these tests.

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Human Tests for Allergy Sensitivity or Tests for Exposure to Allergens

Skin Testing for Allergic Response, Allergies, and Allergic Exposure in Humans

The most common allergy test type performed on humans are skin tests to determine whether or not a person has or will have an allergic response to certain common allergens. Skin tests are quick, reliable, and less costly than blood tests and immunoassay tests discussed at ELISA and RAST. The doctor places a small amount of an allergen on or below the person's skin, using a needle prick, a small round scratch or scarifier, a tiny injection of substance below the skin, or a skin patch - a pad containing the allergen is taped to the skin for 24 hours or longer.

The physician (typically an allergist who specializes in allergies) "reads" the results of the skin test by noting the varying severity of skin reaction (swelling, reddening, itching) at each test site. When the author's cousin, Dr. Edward Friedman, a diplomate allergist, performed these tests on the website author (DJF), he used a round scarifier to make a field of about 12 test sites on the patient's arm, then placing a different test solution on each scratch spot. In less than an hour the variation in reaction among allergens was visibly obvious.

At ALLERGENS in buildings, RECOGNIZING we discuss and provide photos of common indoor allergenic particles found in homes and in the work place. Also see CAT DANDER in buildings. Where toxic, pathogenic, or allergenic mold is a concern in buildings, see MOLD DETECTION & INSPECTION GUIDE and MOLD EXPERT, WHEN TO HIRE.

Accuracy of Skin Tests for Allergies, Including Mold Sensitivity or Mold Exposure Testing

Accuracy of skin testing for allergens is reasonably good, certainly sufficient for an allergist to decide on treatment (or environmental steps such as cleaning and avoidance of exposure to certain allergens). But here are some allergy skin test accuracy considerations readers should keep in mind:

False positive allergy test results: the intradermal (injection) test for allergies can produce false positive results, indicating an allergic response in an individual who has not previously reacted to that allergen in the environment.

False negative allergy test results: we have experience with these conditions that allergy sufferers or anyone who experiences respiratory or apparent indoor air quality complaints associated with spending time in a building:

Limited number of FDA-approved substances for allergy testing: according to Dr. Friedman, at the time of our allergy test experiments, the actual number of substances that are US FDA approved for use in preparation of allergy testing serums was quite small. For example, although there are about 1.5 million mold species, less than ten molds have been approved for use by physicians or drug companies for the preparation of mold testing serums.

While there are likely to be common chemical characteristics among many mold genera and species, making selected very common molds (an individual Cladosporium species, for example) useful in gauging reaction to a wider number of molds from the same mold genera or even among several genera of molds, a negative mold test result, having combined perhaps seven molds to make up the test, can hardly be taken as a guarantee that the individual is really not mold sensitive to any of the remaining 1,399,993 mold genera/species in the world.

Immunoassay Allergy Testing: ELISA and RAST Allergy Tests Humans for Allergen Exposure - The Basics

Here is some basic information about ELISA and RAST tests used on humans to look for exposure to animal allergens. These allergen tests are allergy blood tests designed to be performed on humans (or on animals themselves with even more inaccurate results), not on indoor building samples of dust or debris. Blood tests for allergies look for antibodies in the blood that are formed in response to the individual's exposure to allergens. According to WebMD and some other sources, blood tests for allergies are less sensitive than skin prick or scratch tests, but are used for people who must avoid skin tests for allergies.

ELISA "enzyme-linked immunosorbent assay" (also referred to as ELISA, EIA) is a rapid immunochemical test procedure that involves an enzyme (a protein that catalyzes a biochemical reaction) that tests for hormones, bacterial antigens, and antibodies. ELISA testing also involves an antibody or antigen (immunologic molecules).

The assay procedure is widely used, not just for allergens - even for drug use. MedicineNet provides a detailed definition of ELISA testing. ELISA are popular over RAST (below) probably because they don't require radioisotopes or a radiation-counting apparatus. ELISA tests are indeed quite sensitive and ELISA testing is specific to the particular allergens (or other exposures) under study. In accuracy, ELISA testing is similar in accuracy to radioimmune assay (RIA) tests.

RAST (radioallergoabsorbent testing) is an older allergen test (exposure detection) in popular use for testing humans, radioallergosorbent test, an IgE test: In this test, a sample of blood is taken, mixed with the suspected allergen, and the level of immunoglobulin E (IgE) is measured. IgE is an antibody produced by the immune system that indicates an allergic reaction.

Immunoassay capture testing (ImmunoCAP, UniCAP, or Pharmacia CAP) are other allergy tests used on humans to obtain additional allergy exposure and allergy sensitivity data.

The ELISA and RAST allergen exposure tests are performed on the individual, not on the environment that the individual has occupied. If we're trying to determine which environment is more likely to be contributing to allergen exposure (dander and hair), a dust screen from that environment tells us what we need to know; testing the person who is suffering is pertinent to the physician and the treatment plan, but it does not identify the problem source - the location.

Example: we inspected and tested in an office where an employee complained of severe allergic responses - suspecting that there were animal allergens in the workplace. We collected dust from the workplace, and from her desk, chair, and clothing - nearly all of the animal dander (cats in this case) was on the employee's clothing - the employee was picking up the allergens somewhere other than in the workplace.

Accuracy of ELISA and RAST testing

Sheryl B. Miller and others have raised questions about the actual accuracy of ELISA test results and about the absence of a comparative standard.

Check With Your Doctor About Allergens and About Whether or Not Building Tests for Allergens or Mold are Recommended

Of course since individual sensitivity to allergens varies, we suggest that anyone suffering from allergies and considering steps to further clean their home should also consult with their allergist and their general physician.

  • Safety Warning: if indoor air quality complaints include respiratory distress, headaches, nausea, and similar symptoms, it is important to immediately rule out unsafe heating equipment, chimneys, flues, or carbon monoxide hazards. See CARBON MONOXIDE - CO
  • The types, accuracy, and variability of human tests for allergy sensitivity and allergy or mold exposure are discussed further at ALLERGY TESTS.
  • The combination of allergy testing limitations and occupant complaints that may in some cases justify a building survey for physical particles or other evidence of significant levels of problem allergens, molds, or other conditions is discussed at ALLERGY TEST LIMITATIONS.
  • See MOLD EXPERT, WHEN TO HIRE for advice on determining when it is appropriate and justified to order inspections and tests of a building for mold or allergens.
  • See BIOLOGICAL POLLUTANTS for information about recognizing and removing these indoor contaminants.
  • See ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY for our full list of environmental hazard identification and remedy related to buildings.

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