Do Not Use Blood Tests Alone to Diagnose Food Allergy
A mother came to see me, looking stressed and worried.
Her child had been losing weight and was falling behind on growth chart.
Her pediatrician had written an urgent referral for her to see me.
“Doctor, I have these allergy test results. They say all these foods are causing allergies.”
She showed me the report.
There they were. Beautifully colored numbers, with one positive result after another.
I spent a long time going through the results and explaining what they meant.
Here is what I want you to know:
A positive food allergy blood test does not automatically mean your child is allergic to that food.
When test results are misunderstood, children may end up avoiding foods they can actually eat safely.
In some cases, unnecessary food restrictions can affect nutrition, growth and quality of life.
Let’s look at why this happens—and how food allergies should be assessed.
The Problem with Blood Tests for Food Allergies
Blood tests measure food-specific IgE antibodies, which indicate sensitization but do not necessarily mean a person has a food allergy.
Someone may test positive and still eat that food without any reaction.
This is common in people with eczema, who may test positive to several foods that are not causing their symptoms.
When every positive result is treated as an allergy, children may avoid foods unnecessarily, risking poor nutrition and impaired growth.
The aim is to identify foods that truly cause allergic reactions
Not eliminate every food with a positive test.
Study Warns Against Over-Reliance on Blood Tests
A study published in The Journal of Pediatrics highlights the risks of using blood tests alone to diagnose food allergies:
🔹 89% of oral food challenges (OFCs) showed that children were unnecessarily avoiding foods.
🔹 Many children were on overly restrictive diets, avoiding foods they had previously eaten without issues.
🔹 Failure to thrive was observed in some children due to unnecessary food eliminations.
Dr. David M. Fleischer, the lead researcher from National Jewish Health in Denver, warns:
“The practice of ordering large panels of serum IgE tests and eliminating foods without proper interpretation by an allergist needs to change.”
Why Clinical History Matters
When assessing a possible food allergy, I start by finding out what is happening – not simply the list of positive results.
I want to understand:
- Symptoms: What happens after eating the suspected food?
- Timing: How soon do symptoms appear?
- Reaction severity: Were the symptoms mild, or was there a more serious reaction?
- Previous food exposure: Has the person eaten the food before without problems?
- Pattern of reactions: Do symptoms occur consistently when the food is eaten?
A skin prick test (SPT) or a blood test for specific IgE may help assess the likelihood of an allergy when supported by the history.
When the diagnosis remains uncertain, an oral food challenge (OFC) may be recommended.
Conducted under appropriate medical supervision, it is the gold standard for confirming or excluding many food allergies.
Not everyone needs every test. The appropriate investigation depends on the individual.
Information You Can Use
- A positive test does not always mean an allergy. Results must be interpreted alongside symptoms and food history.
- Do not avoid foods unnecessarily. If you can eat a food without symptoms, do not eliminate it solely because of a positive test.
- Seek specialist advice. An Allergy & Immunology specialist can help determine which tests you need and what the results mean.
- Consider an oral food challenge. When appropriate, this can help confirm whether a food allergy is present.
Need help interpreting food allergy test results? Contact Allergy Immunology Clinic for an assessment.
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