Celery (Api g 7) IgE

Say you've had hives, a swollen throat, or a sudden faint feeling after celeriac soup or a heavily spiced dish, and your celery allergy test came back negative. This result may explain what happened. Api g 7 is a small protein in celery root. Its full name comes from Apium graveolens, the Latin name for celery. This test measures IgE antibodies against that protein. IgE is the antibody your immune system makes when it has decided something is an allergen.

In people with confirmed celery allergy, having these antibodies went with nearly six times the odds of a severe whole-body reaction. Standard celery extract tests can miss this pattern, especially when Api g 7 is the only celery component your antibodies recognize. This is a newer marker without standardized risk cutpoints, so a result here can add useful risk information without settling a diagnosis by itself.

What the Test Measures

Api g 7 belongs to a family of plant proteins called defensins, which plants use to fight off fungi and other attackers. It's concentrated in celeriac, the knobby root form of celery. The test reports how much IgE in your blood binds to this one protein, in kU/L. A detectable amount means you're sensitized, so your immune system has learned to recognize the protein. On its own, that isn't proof you'll react when you eat it.

What sets Api g 7 apart from the better-known celery allergen, Api g 1, is how well it holds up to heat. Api g 1 is heat-sensitive and usually fits the birch-related pattern, where raw celery causes itching in the mouth or throat. Api g 7 starts to unfold only around 74°C and melts at about 100°C, so it largely survives cooking. That's why people sensitized to it can react to cooked celeriac, soups, and processed foods, not only raw celery.

Severe Reactions

The strongest finding comes from a study of 79 people with confirmed celery allergy across several European centers. About half of them, 52%, had antibodies to Api g 7. Compared with celery-allergic people without these antibodies, they had nearly six times the odds of a severe, whole-body reaction rather than mild mouth symptoms.

That estimate rests on a small group, and the plausible range is wide, running from barely raised risk to about 32 times the odds. The direction is clear but the exact size isn't. Even so, the finding fits the protein's biology: an allergen that stays intact after cooking is more likely to keep its IgE-binding shape in soups and processed foods.

What this means for you: if you've ever had more than mouth itching after celery or celeriac, a positive result here moves you into a group that should be prepared for a whole-body reaction and should have an allergist workup. For most people with antibodies, the next reaction may never be severe. For the person whose reaction is, preparation makes all the difference.

Why the Standard Celery Test Misses It

Standard celery allergy blood tests use an extract, a mixture of proteins pulled from the whole vegetable. Api g 7 is poorly represented in these extracts, probably because it's lost during preparation. In the 79-person study, 11 of 12 people sensitized only to Api g 7 tested negative on the commercial celery extract. In the first 8-person report on Api g 7, five people with antibodies to the component had negative celeriac-extract results.

Testing for individual celery proteins closes much of that gap. Adding Api g 7 to a panel of other celery components, Api g 1, Api g 4, and Api g 5, caught 92% of celery-allergic people. An earlier study, before Api g 7 was known, found that component testing raised detection from 67% to 88% compared with extract testing. As of a 2025 review, the major multiplex allergy arrays, ISAC and ALEX, did not include Api g 7.

The Mugwort Connection

Allergists have described celery-mugwort syndrome for decades: people allergic to mugwort, a common late-summer weed, who also react to celery and related spices. Api g 7 turns out to be a main link. It's about 60% identical in amino-acid sequence to Art v 1, the major allergen in mugwort pollen, and IgE levels to the two track each other very closely, with a correlation of 0.86 where 1.0 would be a perfect match.

The direction of that relationship matters. In lab experiments using patients' blood, Art v 1 completely blocked IgE from binding to Api g 7, while Api g 7 only partly blocked binding to Art v 1. That pattern points to mugwort pollen as the usual starting point. People likely become sensitized by breathing in mugwort pollen, and their antibodies then cross-react with the similar protein in celery. If you have weed pollen allergies, you can develop this sensitization without ever having had a problem with celery.

A large Italian study tested 7,176 people for allergen antibodies and found defensin sensitization in 272. Of 90 people tested for Api g 7, 74 were positive. Amb a 4 is a related defensin in ragweed pollen. People sensitized to both mugwort Art v 1 and ragweed Amb a 4 had about seven times the odds of food reactions.

Spices are part of the same picture. In older studies of celery allergy generally, not Api g 7 specifically, celery-sensitive people often reacted to spices from the same plant family, such as caraway, coriander, and fennel. In food challenges, both cooked celery and celery spice triggered reactions in a subset of patients.

Sensitized Is Not the Same as Allergic

The strong mugwort cross-reactivity cuts both ways. In a study of 385 pollen-allergic people, IgE to food allergens was common whether or not people had any food symptoms. So a positive Api g 7 result in someone who eats celery without trouble is a flag worth knowing about, not a diagnosis. The same result in someone with a history of hives, swelling, or breathing trouble after celery carries much more weight.

Read your number along a gradient. Across allergens, the likelihood of a real reaction tends to rise as specific IgE rises, so a strongly positive result deserves more caution than one barely above the detection limit. For Api g 7 specifically, the level at which risk becomes high hasn't been worked out yet.

When Results Can Be Misleading

• Lab and method differences: allergen-specific IgE results often disagree between testing platforms, and the method behind this catalog test isn't specified. Compare your results only against earlier results from the same lab.
• Biologic drugs: dupilumab is a targeted immune drug used for eczema and asthma. It has lowered allergen-specific IgE in food allergy and allergic rhinitis studies, so a low result while you're taking it may understate your earlier sensitization pattern.
• Pollen season: in people with pollen allergies, specific IgE to pollen rises and falls across the season, and nasal allergen exposure raised specific IgE in a birch study. This hasn't been shown for Api g 7, but because mugwort often drives it, note the season when you test.
• Allergen immunotherapy: during allergy shots or tablets, specific IgE to the treated allergen often rises during the first year before falling later. A temporary rise during treatment isn't a sign of worsening.

Tracking Your Trend

A single result tells you whether you're sensitized now. Repeat testing can show whether your own value is changing, which matters most if you have weed pollen allergies, still eat celery without trouble, or are starting immunotherapy or a biologic drug. There is no published Api g 7 trend data yet, so your history still carries more weight than a small movement in the number.

Use the same lab each time and, where possible, test at a similar point in the pollen season so the comparison is fair. A baseline is useful. After that, repeat testing makes the most sense if your symptoms change, your treatment changes, or you're following a known positive result.

What to Do With Your Result

A positive result with any history of reactions beyond mouth itching is the pattern that calls for action. See an allergist for an epinephrine auto-injector prescription and to plan a supervised food challenge, which is the definitive way to confirm food allergy. Until then, it's reasonable to avoid celeriac, celery-containing soups and stocks, and celery spice.

Fill in the picture with companion tests. Mugwort Art v 1 IgE confirms whether pollen is driving your sensitization, and ragweed Amb a 4 IgE identifies the higher-risk combination seen in the Italian data. Celery Api g 1 and birch Bet v 1 IgE point to the milder birch-related form. Celery Api g 6 or peach Pru p 3 IgE point to a separate group of cooking-resistant allergens common in Mediterranean regions.

If your result is negative but you've clearly reacted to celery, don't stop there. Other celery components may explain it, and an allergist can do skin testing with fresh celery, which picks up proteins that commercial extracts miss. A positive result without symptoms calls for companion testing and a careful history, not automatic food avoidance. You don't need to avoid celery you already eat without problems.