Diagnosis and Testing for Allergies:

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Diagnosis or determining whether someone is suffering from allergies or not, begins with the history. The physician or health care provider is interested in knowing the pattern of the symptoms and their relation to any possible allergen exposures. For example in the case of allergic rhinitis one would ask:

  • Do you sneeze or get itchy nose/ eyes during a specific season or all year round?
  • Is it worse at night or during the day?
  • Indoors or outdoors?
  • With exposure to pets or other animals?

Tests are performed when the history points to a possible allergic reaction to a specific allergen. Skin tests and RadioAllergoSorbent blood Tests (RAST) are performed to determine the presence or measure the level of the allergic antibody, IgE, to the allergen.

It should be stressed that a positive allergy test alone does not make the diagnosis of an allergic reaction. The results of the test must be correlated with the patient’s history.

  1. Skin tests the most commonly used form of allergy testing. In this test, an extract of the allergen is placed on the skin, then a superficial puncture or scratch is made at the site allowing contact between the deeper layer of the skin and the allergen.If a person is allergic to that particular allergen, an itchy wheal with surrounding redness will form within 15 minutes. If this “scratch” or epicutaneous test is negative, in the case of airborne or medication allergies, the patient may then go on to get small doses of the allergen injected under the skin, called “intradermal” skin testing. The intradermal test is not recommended for food allergens.
  2. Blood Test or RAST– measures the levels of the allergic antibody IgE in the blood to specific allergens. This test is not as sensitive as the skin test, but is used if a skin test can not be performed because the patient is taking antihistamines, has a rash covering his body, or if he or she had a severe allergic reaction (anaphylaxis) to the suspected allergen.
  3. Challenge Test– In the case of food or medications, even if a person has a negative skin test or blood test, there is still a chance that a person may still have an allergic reaction to the suspected allergen.In this case, challenge tests are performed where the person is given small, increasing doses of the suspected food or medication at regular intervals and under close monitoring to determine if he or she develops any signs or symptoms of an allergic reaction. These tests may be open or blinded where the person and/or the physician may or may not know whether the patient is getting the actual allergen or a placebo to avoid bias.

5 thoughts on “Diagnosis and Testing for Allergies:

  1. Wow, one of the links finally worked! Clicking on the link you left on the PGR post leads to a “page not found” message for me.

    I am still quite confused as to what exactly you disagree with in my article. The four methods of allergy testing I discussed were skin prick testing, physician-supervised elimination and reintroduction of the food, IgE blood tests, and double-blind placebo-controlled food challenges.

    Which of those four testing methods are you referring to as not being scientifically accepted?

    Of course I am not recommending that any patient try to interpret test results without help from a doctor. But what is our recourse when we do not have access to good doctors?

    I am arguing that we need more and better research, and better treatment from doctors. The only way we can get that is by promoting awareness, raising funds, and working for change. I would hope that both doctors and lay people could be involved in that.

    Again, if there are any factual errors in my articles I would be happy to correct them if someone can specifically point them out.


  2. The page you linked to in PGR is chock full of inaccuracies and the link to studies that do not support the points you are trying to make and reveal a lack of understanding of the important medical issues that you make statements about, for example:

    1) You state that”Even life-threatening anaphylactic reactions are likely to be discounted or misdiagnosed.”, and then you link to a study that in fact states that epinephrine is underused in the ER in the treatment of anaphylaxis and does not talk at all about misdiagnosis or underdiagnosis of anaphylaxis.

    2) You state that
    “Many doctors believe that IgE testing is the only accurate way to diagnose allergies. However, such tests are not always accurate.” and then you link to a Pubmed page that does not say this at all, but at most states that the “accuracy of these tests may vary”, which is a far cry from saying that they are not accurate. In fact, the accuracy of skin and RAST tests range from 80-95% when interpreted appropriately.

    3) You state that the sensitivity and reliability of skin tests is as low as 15% but then link to a study comparing atopy patch testing and food skin testing in patients with eczema, which is not always an IgE mediated disease (unlike, asthma, anaphylaxis, and rhinitis). Again, this reveals a lack of understanding of basic allergic mechanisms.

    It is dangerous and irresponsible to make statements about medical issues that you do not fully understand. I suggest you take your own advice and increase your education and awareness about basic allergy issues before making such pronouncements.


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