IgE level: what a raised IgE in your blood means

You are holding a lab report with one line jumping out at you: total IgE, and a number. Your IgE level is raised, it says. And then what? The paper tells you nothing about what you might actually be allergic to.

That is no accident. A total IgE adds up all of your IgE, and that sum simply does not answer the question "am I allergic?".

Let me be blunt. We sell blood tests, and a standalone total IgE is in our view the most wasted blood test in this corner of the market. If you want to know whether you are allergic, your money is better spent elsewhere. Here is what does work.

What is IgE, really?

IgE stands for immunoglobulin E, one of the five antibody classes in your blood. It is the antibody behind immediate allergic reactions. IgE attaches to mast cells in your skin, nose, lungs and gut. When the allergen turns up, it binds that IgE and those mast cells release histamine. Within minutes you get itching, sneezing or swelling.

The World Allergy Organization therefore treats allergy as more than an antibody. Clinically relevant symptoms belong to it, triggered by that one specific allergen (PMID 32128023).

Histamine is the end product of this story, not the cause. How histamine works in your body, and what blood testing can and cannot say about it, sits in the overview on histamine intolerance and what your blood shows.

What is a normal IgE level?

There is no number that holds everywhere. Normal values for IgE vary strongly between laboratories, and they shift with age: children run lower, adults higher. In adults you often see an upper limit somewhere around 100 kU/l, though labs apply ranges from roughly 20 to 150. The limit printed on your own result is the only one that counts.

So treat the number above as indicative, not as a rule. The lab that spun your tube sets your reference range.

The unit is kU/l, kilo-units per litre. The lab uses that same unit for specific IgE, which makes things more confusing. Two completely different tests, the same kind of number on your paper.

And here is the part that really matters: a total IgE inside the normal range does not rule out an allergy.

Total IgE or specific IgE: which one do you need?

Almost always specific IgE. Total IgE adds up all your IgE, whatever it is aimed at. Specific IgE (sIgE) measures your IgE against one allergen: birch pollen, peanut, house dust mite, cat dander. Only that second number can say something about an allergy, and even then only alongside your symptoms.

The Dutch association for clinical chemistry and laboratory medicine (NVKC) is clear about this in its Zinnige Diagnostiek advice on allergy testing. Advice number one reads, literally: do not determine total IgE in serum when allergy is suspected. There is no good cut-off that separates allergic from non-allergic people, and a normal total IgE does not rule out allergic disease.

That is exactly what I meant in the intro by a wasted test.

An sIgE number is not a universal scale either. For cat dander, values in class 3 (3.6 to 17.5 kU/l) often go with substantial symptoms, according to the NVKC. For dog dander you usually only see strong symptoms from class 4 upwards (17.6 to 50 kU/l). Same number, different meaning.

What an IgE result does and does not prove around food, we work out separately in the article on the food allergy test.

Does a raised IgE level mean you are allergic?

No. A raised IgE level means your immune system is making more IgE, nothing more. It does not say what that IgE is aimed at, and it does not say whether it gives you symptoms. An allergy only exists when sensitisation and symptoms coincide, triggered by that one allergen (PMID 32128023).

Take two people with exactly the same number: a total IgE of 180 kU/l.

The first is 34 and sneezes his way through the grass pollen every May, with itching eyes and a blocked nose. His specific IgE against grass pollen is clearly positive. Number, symptoms and season all point the same way, and that fits an allergy.

The second is 41 and has had eczema all her life. She reacts to nothing, eats everything without trouble, and has no hay fever symptoms at all. Her 180 kU/l almost certainly comes from her atopic skin. Same number, no allergy.

The symptoms decide, not the lab.

The research says the same thing in other words. sIgE tests are excellent at identifying a sensitised state, but a positive result does not always equate with clinical allergy (PMID 22201146). These tests only denote sensitisation; atopy and allergy are two different phenomena (PMID 35386974). A diagnosis leaning on a test result alone gets it wrong with some regularity.

What else can a high IgE mean?

Quite a lot. IgE can rise with allergy, but also with a parasitic infection, with eczema and atopy, with smoking and with a handful of rare conditions. In people without a single symptom the value can simply sit naturally on the high side. A high result is a question, not an answer.

The non-allergic explanations we come across most often in practice:

• Parasitic infection: worms trigger a strong IgE response. Rare in the Netherlands, but relevant after a stay in the tropics.
• Atopic eczema: can lift total IgE considerably without a single allergen being identifiable.
• Smoking: smokers have a higher average total IgE than non-smokers.
• Rare conditions: some immune deficiencies and blood disorders come with a strongly raised IgE.

Eosinophils often move alongside these processes. That is a type of white blood cell counted as raised from roughly 450 to 550 cells per microlitre. The causes span allergy and asthma, drug reactions, parasites, autoimmune disease and, rarely, blood disorders (PMID 27866580). What a rise there can mean sits in the article on high eosinophils.

Without symptoms, a raised IgE on its own is no reason to panic.

What do you do with your IgE result?

Start with your symptoms, not with your number. Write down what you feel, when, where and after which exposure. Take that story and your result to your GP. From there you can pick, on purpose, which specific IgE makes sense, instead of ordering a broad panel blind. IgE in allergy only works that way.

One thing stands entirely apart from any laboratory. Shortness of breath, swelling of your lips, tongue or throat, or other signs of anaphylaxis, is acute care: call 112 or go to the out-of-hours GP service. Never wait for a blood result in that situation.

For targeted testing the route is reasonably clear. With recurring nose, eye or airway symptoms, the inhalation allergy panel is the obvious choice. With an immediate reaction after eating something specific, the food allergy panel fits better. To see whether your immune system is moving along, you add eosinophils.

You pick those markers individually through building your own blood test. I would rather see your money land there than in a standalone total IgE that never answers your question.

Thuisarts, the patient site run by the Dutch GP body NHG, follows the same order in allergy: the story of your symptoms drives the testing, not the other way round. How to read a result more broadly sits in understanding your blood test results. If you suspect pollen is the culprit, carry on with the hay fever test.

References

1. Sicherer SH, Wood RA. Allergy testing in childhood: using allergen-specific IgE tests. Pediatrics. 2012;129(1):193-197. PMID 22201146.
2. Ansotegui IJ, Melioli G, Canonica GW, et al. IgE allergy diagnostics and other relevant tests in allergy, a World Allergy Organization position paper. World Allergy Organ J. 2020;13(2):100080. PMID 32128023.
3. Testera-Montes A, Salas M, Palomares F, et al. Diagnostic Tools in Allergic Rhinitis. Front Allergy. 2021;2:721851. PMID 35386974.
4. Kovalszki A, Weller PF. Eosinophilia. Prim Care. 2016;43(4):607-617. PMID 27866580.
5. NVKC. Zinnige Diagnostiek: overwegingen bij het aanvragen van allergiediagnostiek. Available via nvkc.nl.
6. NHG and Thuisarts. Patient information on allergy and blood testing. Available via thuisarts.nl.

Every blood test result at Vitalcheck includes a professional assessment by a BIG-registered doctor. A blood value is not a diagnosis: always discuss treatment decisions with your GP.