Explanation

Tree pollen mix (allergy): what is measured?

The test measures, in one go, IgE antibodies against a fixed mix of pollen from 5 trees that flower in late winter and spring: alder, birch, hazel, oak and willow (goat willow). Alder and hazel flower earliest, often from January; birch, oak and willow follow later in spring. IgE is the type of antibody that, in an allergic reaction, triggers mast cells to release histamine; the body only makes these antibodies after it has previously been in contact with an allergen, and this is called sensitization. Because the 5 trees are tested together, the result gives one number and a verdict of positive or negative, but not which tree the antibodies are directed against. Pollen from alder, hazel and oak resemble birch pollen, so antibodies against these trees often occur together. Pollen from other trees, such as ash, plane or pine, is not in the mix.

What can it detect?

Sensitization to tree pollen: the body has made IgE antibodies against pollen from at least one of the 5 trees in the mix
An indication of whether symptoms of the nose, eyes or airways in late winter and spring may be caused by tree pollen

Result

What does the result mean?

Positive result

A positive result means that you have IgE antibodies against pollen from at least one of the trees in the mix: sensitization. That is not the same as an allergy, and the test does not say which tree the antibodies are directed against. With symptoms such as sneezing, a blocked or runny nose, itchy or watery eyes or shortness of breath in spring, a positive result fits hay fever from tree pollen; according to the Longfonds (Dutch lung foundation), trees such as hazel, alder and birch cause symptoms from January to May. Some people with hay fever also get itching or a burning feeling in the mouth or throat when eating, for example, apple or hazelnut. In people without such symptoms, a positive result only means that the antibodies are there; no treatment follows.

Negative result

A negative result means that no IgE antibodies against pollen from the 5 trees were found. Hay fever from these trees is then much less likely. An allergy to trees that are not in the mix, such as ash or plane, is missed. Symptoms later in the year fit grass pollen (May to August) or weed pollen such as mugwort (late summer) better, and house dust mite, animals or molds can cause symptoms all year round. Nasal symptoms can also have a non-allergic cause.

After an abnormal result

The GP mainly looks at the history: in which months and where the symptoms occur, and whether there are symptoms in the mouth after eating fruit or nuts. With a positive result and matching symptoms, advice follows to reduce contact with pollen, such as keeping windows closed on dry, sunny days, and if needed medication for the nose and eyes. A test for single tree pollens can show which trees are involved; with a lot of symptoms despite medication, an allergist or ENT specialist can discuss immunotherapy.

Reliability

How reliable is the test?

A positive IgE result shows sensitization, not allergy: it only says that there are antibodies, not that you get symptoms from them. The Dutch medical specialists' guideline (FMS) on upper airway allergy recommends choosing an IgE test for single allergens based on the history of the symptoms; a mix tests more allergens at the same time, so a low sensitization without clinical meaning can more easily make the result positive. The mix is therefore mainly a first step: a negative result makes hay fever from these trees less likely, a positive result can be looked into further with a test for single tree pollens. Symptoms that fit the flowering of trees make a positive result more meaningful.

What can affect the result?

Sensitization without symptoms is common; the result can only be interpreted together with the history of the symptoms.
The test does not say which tree you react to; that requires a test for single tree pollens, and even that does not always show which tree causes the symptoms, because of cross-reaction between birch, alder, hazel and oak.
Antibodies against tree pollen often also give a positive IgE result for nuts, fruit or soy without a real food allergy.
Laboratories use different mixes, measurement methods and cut-off values; results from different labs cannot be compared one to one.

Who it is for

Who is the test useful for?

Useful for

Useful with symptoms of the nose, eyes or airways that come back every year in late winter and spring, especially outdoors on dry, sunny days, and with itching in the mouth or throat after eating apple or nuts in someone with hay fever. In people without such symptoms, the test adds nothing: sensitization without symptoms is not a disease and is not treated.

How common is it?

Hay fever is common and often starts at a young age. According to the Longfonds (Dutch lung foundation), trees such as hazel, alder and birch cause symptoms from January to May. Sensitization is more common than the allergy itself.

Longfonds and Thuisarts.nl; no Dutch prevalence figure has been checked

Drawbacks and risks

A positive result, together with positive results for nuts or fruit due to cross-reaction, can lead to unnecessarily avoiding foods that you eat without serious symptoms.
A negative result does not rule out symptoms in spring from other trees or other causes.

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