Explanation

Grass pollen mix (allergy): what is measured?

The test measures, in one go, IgE antibodies against a fixed mix of pollen from 5 grass species that grow widely in meadows, roadsides and lawns in the Netherlands: cocksfoot, meadow fescue, perennial ryegrass, timothy grass and smooth meadow grass. 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 grasses are tested together, the result gives one number and a verdict of positive or negative, but not which grass species the antibodies are directed against. With grasses this matters less than with other mixes: the pollen of these grasses are very similar, so antibodies against one grass usually also fit the others. Pollen from rye, a cereal, is not in the mix.

What can it detect?

Sensitization to grass pollen: the body has made IgE antibodies against pollen from at least one of the 5 grass species in the mix
An indication of whether symptoms of the nose, eyes or airways in late spring and summer may be caused by grass 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 grasses in the mix: sensitization. That is not the same as an allergy, and the test does not say which grass species the antibodies are directed against. With symptoms such as sneezing, a blocked or runny nose, itchy or watery eyes or shortness of breath in the grass season, a positive result fits hay fever from grass pollen; according to Thuisarts.nl, these symptoms start in April or May and are usually worst between May and August. 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 grasses were found. Hay fever from grass pollen is then much less likely, because the pollen of most grasses resemble those of these species. Symptoms in another season fit something else better: tree pollen mainly causes symptoms in spring, pollen from weeds such as mugwort in late summer, 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. 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. With a lot of symptoms despite medication, an allergist or ENT specialist can discuss immunotherapy, where a test for single allergens helps determine which pollen it targets.

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. With grass pollen this weighs less, because the grasses in the mix are very similar: the mix mainly shows whether you are sensitized to grass pollen in general. The result can only be interpreted together with the season in which you have symptoms.

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 grass species you react to; because of the strong cross-reaction between grasses, a test for a single grass usually adds little to that.
Pollen from trees and weeds, house dust mite, animals and molds are not tested.
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 spring and summer, especially outdoors on dry, sunny days. The result then helps determine whether grass pollen may be the cause. If your symptoms fall in another season or last all year, a test for other allergens says more. 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), the grass pollen period from May to August is the period with the most symptoms for many people. 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 without symptoms can cause unnecessary worry or unnecessary measures, while sensitization without symptoms does not need treatment.
A negative result does not rule out symptoms in summer; other pollen, molds and non-allergic causes also give nasal symptoms.

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