One of the most frustrating things as a parent is when we suspect that something our child is eating is causing a problem, but we aren’t sure what. The two most common options for assessing food sensitivities are the elimination diet and allergy blood tests. I’m going to cover the pros and cons of each and explain why in most cases, I prefer the elimination diet over allergy blood tests.
How Does An Elimination Diet Work?
The concept behind elimination diets (aka food elimination and rechallenge tests) is simple. Suspect foods are removed from the diet for a prescribed period of time, then reintroduced one at a time. If symptoms arise, they are recorded.
If a symptom disappears when a food is removed and reappears when it is reintroduced, then we conclude that there’s a sensitivity to that food.
How Do Allergy Blood Tests Work?
The two most common types of allergy blood tests are IgG and IgE tests. To conduct these tests, a lancet is used to pierce the finger (or heel in babies) and blood is dropped onto a collection card. Once the blood is dried, the sample is mailed to a lab. Results may take days, weeks, or even months to come back depending on the lab used. The cost is usually between $100-$500 depending on the number of allergens tested.
The idea is that if IgG or IgE antibodies to a food are present in the blood, it means that the body will mount an allergic reaction to that food when it is consumed.
Note: in my practice, I find that IgE tests provide much more useful and accurate results than IgG tests.
Pros And Cons Of The Elimination Diet
Pros Of The Elimination Diet
- Response of the body is more reliable and useful than blood test results
- Can identify both food allergies and other adverse food reactions (see below)
- Low cost
Cons Of The Elimination Diet
- Difficult to test a wide range of foods
- Difficult to make the diet changes necessary for food elimination, especially with picky eaters and neurodiverse children
- The root cause of the symptoms may be unclear. This is a big problem with gluten. If a gluten sensitivity is found, further testing to determine if celiac disease is present is wise.
- Contraindicated for people with eating disorders in many cases
Types Of Food Reaction Identifiable Using An Elimination Diet
- Food allergies
- Bladder irritants
- Stimulant or other mood altering foods
- Nightshade sensitivity
- FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) sensitivity
- Lactose intolerance
- Tyramine sensitivity for migraine
- Salicylate sensitivity
- Histamine intolerance
- Sulfite sensitivity
- And other less common sensitivities
Pros And Cons Of Allergy Blood Tests
Pros Of Allergy Blood Tests
- Can quickly and easily test a wide range of foods
- Can detect rare and unusual food sensitivities
- It is clear that the cause of the symptoms is an allergic reaction, which helps direct treatment
Cons Of Allergy Blood Tests
- Painful and invasive, especially for younger children and babies
- Not useful if leaky gut is present (usually all foods come back positive)
- Not useful for foods that aren’t regularly consumed
- Test results can be confusing to interpret
- Cost can be high
- Can only detect food allergies, not all the other types of sensitivity
- High rate of false positive and false negative results means that an elimination diet and rechallenge is usually necessary to confirm results
- Unreliable for children under 2 years of age
- Unreliable for people using immunosuppressive therapies
Choosing Between Elimination Diet and Allergy Blood Tests
There are five main factors to consider when choosing between the elimination diet and food allergy blood tests:
Cost of the tests
If cost is a concern, the elimination diet is the less expensive option.
Feasibility of the tests
The challenge of the elimination diet is in preparing food that is free of the sensitivities that are being assessed. This requires willpower, time, energy, and cooperation from all family members. The challenge of the food sensitivity test is in the blood draw which can be especially difficult and painful for younger children.
Types of reaction
Elimination diets can be designed to test for a number of types of food sensitivity. Blood allergy tests only test for allergic reactions.
Reliability of the tests
Done correctly, elimination diets give a reliable reflection of the body’s response to specific foods while blood allergy tests tend towards many false positives and false negatives.
Baseline health status
Age, immune status, gut health, and relationship to food all need to be taken into account when choosing an assessment.
Summary
Elimination diets and blood allergy tests are two common ways to assess food sensitivities. There are pros and cons to both types of assessment, but in my practice I find that elimination diets are much more useful than blood allergy tests. If an allergy or sensitivity to gluten is detected, further testing to rule celiac disease in or out is warranted.
References:
Mullin, G. E., Swift, K. M., Lipski, L., Turnbull, L. K., & Rampertab, S. D. (2010). Testing for food reactions: the good, the bad, and the ugly. Nutrition in clinical practice : official publication of the American Society for Parenteral and Enteral Nutrition, 25(2), 192–198. https://doi.org/10.1177/0884533610362696
Chinthrajah, R. S., Tupa, D., Prince, B. T., Block, W. M., Rosa, J. S., Singh, A. M., & Nadeau, K. (2015). Diagnosis of Food Allergy. Pediatric clinics of North America, 62(6), 1393–1408. https://doi.org/10.1016/j.pcl.2015.07.009
Atkinson, W., Sheldon, T. A., Shaath, N., & Whorwell, P. J. (2004). Food elimination based on IgG antibodies in irritable bowel syndrome: a randomised controlled trial. Gut, 53(10), 1459–1464. https://doi.org/10.1136/gut.2003.037697
Wong, A., White, H., Plant, A., Shipman, A. R., & Shipman, K. E. (2022). Issues surrounding consumer-bought food-allergy testing. Clinical and experimental dermatology, 47(3), 547–552. https://doi.org/10.1111/ced.14978
Gerez, I. F., Shek, L. P., Chng, H. H., & Lee, B. W. (2010). Diagnostic tests for food allergy. Singapore medical journal, 51(1), 4–9.
