Celery (Api g 6) IgE Test · Blood

If you have reacted to celery, or to spices and pollens that often travel with it, the question is rarely whether you are sensitized. It is which celery protein your immune system has locked onto, because different proteins carry different risks. Api g 6 (a celery non-specific lipid transfer protein) is one of several molecular pieces of celery that allergy testing can isolate.

This test measures antibodies in your blood that target Api g 6 specifically. It is one part of a larger map of celery sensitization, and current research suggests it carries less diagnostic weight than other celery components, but it can still add useful texture when interpreted alongside related markers.

What This Test Actually Measures

Celery allergy is not a single condition. It is a family of reactions driven by different celery proteins, each with its own behavior. The major celery components include Api g 1 (a birch-pollen-related protein), Api g 2 and Api g 6 (both lipid transfer proteins, a family of stable plant proteins that resist heat and digestion), and Api g 7 (a defensin, which is a small, very stable antimicrobial peptide). This blood test isolates IgE (immunoglobulin E, the antibody class that drives allergic reactions) directed at Api g 6.

A positive result means your immune system has produced antibodies recognizing this specific celery protein. It does not by itself confirm that you will react when you eat celery, and it does not tell you how severe a reaction would be. It is one molecular signal among several that, taken together, help map your celery sensitization pattern.

Where Api g 6 Fits in Celery Allergy Diagnosis

The honest scientific picture is that Api g 6 plays a smaller role than the other celery components in current diagnostic work. In a Swiss study of 79 well-characterized celery-allergic patients, a combination of Api g 1.01, Api g 1.02, Api g 4, Api g 5, and Api g 7 reached 92% sensitivity for diagnosing celery allergy, while the two lipid transfer proteins Api g 2 and Api g 6 were described as not relevant in that population.

In an Italian cohort of 90 patients with defensin sensitization, about 82% had specific IgE to Api g 7, 11% to Api g 1, and 21% to the lipid transfer proteins (Api g 2 or Api g 6 grouped together). The Api g 7 defensin pattern was the dominant signal for the mugwort-celery-spice syndrome, a cross-reactivity pattern where mugwort pollen allergy spills into food reactions with celery and spices.

Lipid Transfer Proteins and Reaction Severity

Lipid transfer proteins are stable. They survive cooking and stomach acid, which is why sensitization to them can sometimes drive whole-body reactions rather than only mouth-and-throat itching. In the Italian cohort, lipid transfer protein sensitization, specifically Api g 2, was strongly associated with severe systemic reactions. The studies group Api g 6 with Api g 2 as part of the lipid transfer protein family but do not isolate Api g 6's individual clinical impact.

What this means for you: if you test positive for Api g 6, treat it as a signal that your immune system has produced antibodies against a stable celery protein family that has been associated with more serious reactions in other family members. The evidence does not let you draw a sharp line about Api g 6 alone, but the lipid transfer protein family pattern is worth investigating further with an allergist.

Mugwort-Celery-Spice Syndrome

Many people with celery allergy got there through their nose first. Mugwort pollen contains a defensin called Art v 1, which closely resembles celery's Api g 7. The immune system, having learned to recognize Art v 1, can then react to celery and to spices in the same plant family, such as carrot, parsley, anise, and coriander. In Italian patients, co-sensitization to mugwort Art v 1 and ragweed Amb a 4 marked roughly seven times the odds of systemic food reactions compared with mugwort sensitization alone.

Api g 6 is not the driver of this syndrome. If you are testing for celery sensitivity because of pollen-food cross-reactions, an Api g 6 result is one data point, and Api g 7 plus the mugwort and ragweed defensins typically carry more diagnostic weight.

Where This Test Adds Value

Component-resolved testing splits a whole food extract into its individual proteins so you can see which one your immune system actually targets. In one celeriac study, switching from a whole-extract test to component testing raised diagnostic sensitivity from 67% to 88%. Api g 6 is part of that broader molecular map. On its own it adds less than Api g 1, Api g 5, or Api g 7, but as one piece of the picture it can help you and an allergist understand whether your sensitization sits in the lipid transfer protein family, which has been linked to more systemic reaction patterns.

Why a Single Reading Is Not Enough

This is a research-grade marker. There is no standardized clinical cutoff that separates a meaningful Api g 6 IgE result from a meaningless one, and the major celery allergy studies have specifically described Api g 6 as not relevant for diagnosing celery allergy in their cohorts. That makes a single reading hard to interpret in isolation.

Tracking your value alongside the rest of your component panel matters more than any one number. Get a baseline, retest in 3 to 6 months if you are pursuing immunotherapy or making other changes affecting your allergy biology, and at least annually if you have known pollen-food cross-reactivity. Watch the trend across the full celery component panel, not Api g 6 alone.

What to Do With an Out-of-Pattern Result

A positive Api g 6 by itself should not drive a major change in what you eat. The next step is to order the rest of the celery component panel (Api g 1, Api g 2, Api g 5, Api g 7) plus the relevant pollen components (mugwort Art v 1 and Art v 3, ragweed Amb a 4, birch Bet v 1, and peach Pru p 3 as a lipid transfer protein reference). The pattern matters more than any single value.

Combinations to discuss with an allergist: lipid transfer protein sensitization (Api g 2 and Api g 6, often with peach Pru p 3) suggests a Mediterranean-pattern food allergy worth taking seriously. Api g 7 with mugwort Art v 1 points toward the mugwort-celery-spice syndrome. Api g 1 with birch Bet v 1 typically points to milder, mouth-limited reactions. Skin prick testing and, in some cases, a supervised oral food challenge are the standard ways to translate sensitization into a clinical diagnosis.

When Results Can Be Misleading

A positive IgE result confirms sensitization, not allergy. You can have antibodies to Api g 6 in your blood and still eat celery without symptoms. Two factors most commonly muddy interpretation:

• Cross-reactivity with other lipid transfer proteins: because Api g 6 belongs to a protein family found in many plants, a positive result may reflect sensitization that originated elsewhere (peach is a common primary sensitizer) rather than a true celery-driven response.
• Single-component interpretation: the major celery allergy studies have found Api g 6 not relevant on its own for diagnosing celery allergy, so a positive Api g 6 without context from the rest of the celery and pollen component panel can mislead you about real-world risk.

For a celery sensitization workup, the result you should act on is the pattern across all celery and relevant pollen components, not Api g 6 alone.