Positive Test ≠ Allergy: How to Read Food Allergy Results Without Panic

The Scenario I See All the Time

One of the things that happens so many times in my clinic is a patient will come in and hand me test results. These are valid test results for food allergies—often a panel ordered by a pediatrician—where many items are slightly positive. The family is then told to avoid everything on the list.

But the parent will say, “My child is eating most of these foods.” My question becomes: why were they tested in the first place? The answer is often, “I don’t know,” and now they’re confused about what to feed their child.

We’re Talking About Valid Tests (IgE), Not IgG

In previous episodes, we talked about unvalidated tests (IgG). Here, we’re talking about validated IgE tests—done as blood tests or skin tests. Families arrive with conflicting results: “They tested positive to all these things, so they must have these allergies.” Wrong.

The Immune Edit: Positive ≠ Allergy

Even with legitimate, validated allergy tests, a positive test does not equal allergy.

A test result must be interpreted with the patient’s history. Two patients can have similar IgE numbers but very different real-world reactions. History is critical. IgE tests provide one piece of the puzzle—they are not the puzzle.

What IgE Results Actually Mean

You’ll see people online comparing numbers like it’s a scoreboard: “My child’s value is over 100, so it’s worse.” That’s not how this works.

A legitimate IgE food test tells us the likelihood of reacting on exposure—that’s it. It does not tell us:

• How much food will trigger a reaction
• What kind of reaction will occur
• How severe a reaction will be

Again, it’s likelihood, and only one data point among many.

Why a Child Might Tolerate a “Slightly Positive” Food

IgE results don’t account for tolerance mechanisms such as:

• IgG4 (a subtype we measure during food allergy treatment to track increasing tolerance)
• TGF-β and IL-10 (tolerance-promoting immune signals)

Two kids with similar IgE levels can have very different levels of these tolerance markers, different histories (e.g., eczema or not), and therefore different risk profiles. That’s why one child tolerates a food despite a slight IgE positivity while another does not. History ties it together.

Side note on IgG: many companies market IgG as “sensitivity” testing. In clinical allergy care, rising IgG4 often reflects tolerance, not reactivity. We track IgG4:IgE ratios during treatment for that reason.

Broad Panels Create Problems

Food allergy testing should be targeted based on history—not broad panels. Major allergy societies recommend against broad food panels. We use specific tests to support what the history suggests, not to cast a wide net that creates confusion and unnecessary avoidance.

Limits of Each Test Type

Blood (specific IgE) and skin testing can provide similar information in theory. In practice, skin testing adds variables:

• Amount of allergen on the device
• Pressure applied
• Individual skin reactivity

When a test already has known limitations (including false positives), adding more variables can confound interpretation. That’s why I often favor blood testing consistency in many scenarios, while recognizing both methods have a role.

A Promising Tool: Basophil Activation Testing

Basophil activation tests (BAT) expose a patient’s cells to varying food concentrations to see at what level the cells “degranulate” (release allergic mediators). It’s promising, available at select centers, but not yet widely accessible.

What to Ask For (and Push Back On)

• Do: Use history-driven, targeted testing.
• Don’t: Accept broad allergy panels—that’s a red flag for limited expertise. Consider a second opinion.

When reviewing results, look beyond specific food IgE values:

• Consider total IgE and environmental allergy burden
• Consider tolerance indicators (e.g., IgG4 trends if you’re in treatment)
• Anchor everything to actual exposure history and symptoms

The Bottom Line (Your Immune Edit)

• A positive IgE result does not equal a clinical food allergy.
• Always interpret results in the context of the person and their history.
• Don’t compare your (or your child’s) numbers to someone else’s—cases are not interchangeable.
• If someone wants to order a broad panel, ask for specific tests guided by history—or get a second opinion.