The Challenges of Conventional Allergy Testing

Allergietest PricktestWhen I was in my twenties, I experienced what I can only imagine is a very common scenario at the doctors office. I had an extremely reactive nose, that would get stuffed up after most of my meals and some mornings I woke up with eyelids so puffy and swollen, I could barely see through them. I did what anyone would do; I went to my doctor and she referred me to an allergy specialist who performed a skin prick test. I was excited to finally identify what exactly was causing my very aggravating symptoms but much to my dismay, I didn’t react to anything in the prick test and was told that I was completely allergy-free.

As you can imagine, this was very discouraging to me, as the symptoms were clearly present — one look at me in the morning and my swollen eyes, and you could see my body was reacting and waging a battle against something! So I did my own research, and quickly learned that NO allergy test is solely diagnostic for allergies and that the skin prick test ONLY tests for what (for the sake of simplification) I’ll refer to as ‘true allergies.’ The prick test doesn’t identify potential food sensitivities and delayed food reactions, which cause very real symptoms, and are thought to be more common than ‘true allergies.’

‘True Allergies’

A ‘true allergy’ occurs when your immune system misidentifies an otherwise benign substance as harmful, and it releases IgE antibodies in response to the substance that is perceived as a threat. The IgE antibodies then travel to cells, which release the chemicals that are responsible for allergy symptoms, such as histamine. ‘True allergies’ can cause anaphylactic responses, which can be fatal.

Food sensitivities and Intolerances

Food intolerances and what we refer to as food sensitivities are different from IgE reactions. Food intolerances are non-immune mediated; a good example of this is lactose intolerance, which is the result of lowered production of the lactase enzyme required to digest lactose in the small intestine. Food sensitivities are still less well understood, with some evidence that the IgG4 antibody may lie at the heart of the reaction. However, not all health professionals support the IgG4 hypothesis while acknowledging that food reactions are occurring. The symptoms of food sensitivities may show up immediately or up to 24 hours after the food is ingested and they have been associated with an array of chronic health conditions, including asthma, arthritis, fibromyalgia, chronic fatigue syndrome, and IBS. Food sensitivities can produce similar symptoms to ‘true allergies’ but they can cause a wide array of additional symptoms as well, including stomach upset, bloating, sweating, diarrhea, constipation, mouth ulcers, headaches, an inability to concentrate, anxiety, fatigue, food cravings and general feelings of unwellness.

The Skin Prick Test (SPT)

This is by far the most common allergy test used amongst medical professionals, and it can be a very useful tool for identifying ‘true allergies.’ The drawback is that 50-60 percent of all SPTs yield false positive results, meaning they show that you are allergic to something that you really aren’t allergic to. The other problem is that they don’t identify food sensitivities or delayed food reactions.

The RAST Blood Test

A radioallergosorbent, or RAST test, involves taking a blood sample in order to measure levels of food-specific IgE antibodies. Similar to the SPT, blood tests can yield false positive results, they can also cause excessive bleeding, and hematomas, and they do not identify food sensitivities.

Oral Food Challenge Test

This test involves consuming a very small amount of the suspected food allergen under the supervision of a doctor, who then watches for symptoms to appear. The drawbacks here are that severe allergic reactions can occur, the test doesn’t identify delayed food intolerances, the ‘placebo’ effect can happen if the patient suspects what they are swallowing is something they are allergic to, and biases can occur on the part of the doctor. The last two issues can be circumvented by performing a ‘double-blind’ test where neither you nor your doctor knows what you are consuming (a third party is present to monitor).

An Elimination Diet

This involves removing all suspect foods from your diet for a set amount of time (often three weeks). This is considered the gold standard diagnostic tool for adverse food reactions but it should not be performed without the guidance of a qualified health professional. The downside is it can be hard for many people to stick to the diet and exposure to non-food allergens during the reintroduction phase can cause the patient to falsely believe it is the food item that is causing a return of their symptoms.

Additional Tests

Reflexology testing, hair strand tests, electrodermal testing, pulse testing,

Vega testing, IgG testing and reflexology are additional methods used to identify adverse food reactions (most often to identify sensitivities). However, these tests have not been scientifically validated and are not recommended as they can be costly and their accuracy is unproven.

Our Recommendation:

Getting to the bottom of adverse food reactions requires working with a skilled practitioner who will use both laboratory testing and a thorough medical and nutritional history to identify potential culprits. We recommend you keep a detailed journal of what you eat plus any and all symptoms that you experience for 2 weeks. Bring your journal to your practitioner and work with him or her to identify the offending items. Once your diagnostic process is complete, find guidance in creating a healthy, balanced diet based around your specific food restrictions by booking an online consult with one of our expert nutritionists: http://ow.ly/t5KNJ

Recommended reading:

Joneja, Janice Vickerstaff. Dealing with Food Allergies: A Practical Guide to Detecting Culprit Foods and Eating a Healthy, Enjoyable Diet. Bull Publishing Company, 2003.

Endnotes:

  1. American Academy of Allergy Asthma & Immunology. Immunoglobulin E (IgE)
  2. Better Health Channel. Food Allergy and Intolerance.
  3. Australian Society of Clinical Immunology and Allergy. Food Intolerance.
  4. FARE Food Allergy Research & Education. Skin Prick Tests.
  5. National Institute of Allergy and Infectious Diseases. Food Allergy.
  6. Australian Society of Clinical Immunology and Allergy. Allergy Testing.