Explanation

Inhalant allergy screen: what is measured?

The test measures, in one go, IgE antibodies against a fixed mix of 8 allergens that you breathe in: house dust mite (Dermatophagoides pteronyssinus), cat and dog dander, pollen from timothy grass, rye, birch and mugwort, and the mold Cladosporium herbarum. 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 8 allergens are tested together, the result gives one number and a verdict of positive or negative, but not which allergen the antibodies are directed against. The mix does not cover all inhalant allergens: among others, other molds such as Alternaria, horse, rabbit and rodents, and pollen from alder, hazel, oak or plantain are not included.

What can it detect?

Sensitization to at least one of the 8 tested inhalant allergens: the body has made IgE antibodies against one or more of them
A first indication of whether symptoms of the nose, eyes or airways may have an allergic cause

Result

What does the result mean?

Positive result

A positive result means that you have IgE antibodies against at least one of the allergens in the mix: sensitization. That is not the same as an allergy, and the test does not say which allergen the antibodies are directed against. With symptoms such as sneezing, a blocked or runny nose, itchy eyes or shortness of breath, a positive result fits an allergic cause; which allergen it is only becomes clear from a test for single allergens, chosen based on when and where the symptoms occur. In people without 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 the tested allergens were found. An allergy to the house dust mite, pets, pollen or mold in the mix is then less likely. The test does not rule out everything: an allergy to an allergen that is not in the mix, such as horse, rodents, the mold Alternaria or pollen from alder and hazel, is missed, and food allergy is not tested with this test. Symptoms of the nose and eyes can also have a non-allergic cause, such as irritation from smoke and odors or chronic sinusitis.

After an abnormal result

With a positive result, the GP looks at the history: when and where the symptoms occur. If needed, an IgE test for single allergens follows to determine which allergen it is, followed by advice to limit contact with it and possibly medication for the nose or eyes. With symptoms that are not controlled this way or with asthma, referral to an ENT specialist, lung specialist or allergist may follow.

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 test is therefore mainly a first step: a negative result makes an allergy to the tested inhalant allergens less likely, a positive result calls for a follow-up test for single allergens.

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 allergen is the cause; that requires a test for single allergens.
Allergens that are not in the mix and food allergens 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 where you want to know whether an allergy may be behind them, such as sneezing, a blocked or runny nose, itchy or watery eyes or shortness of breath, that come back in a certain season, indoors or around animals. If you already have a clear suspicion, for example symptoms only in spring or only around a cat, a test for that single allergen says more. In people without symptoms, the test adds nothing: sensitization without symptoms is not a disease and is not treated.

How common is it?

Allergy to airborne substances, such as pollen (hay fever), house dust mite and pets, is common in the Netherlands. Sensitization is even more common than the allergy itself: some people with antibodies have no symptoms at all. Allergic nasal symptoms regularly go together with asthma or eczema.

Thuisarts.nl and the FMS guideline on upper airway allergy; no Dutch prevalence figure has been checked

Drawbacks and risks

A positive result without symptoms can lead to unnecessary measures, such as giving away a pet or replacing bedding, while sensitization without symptoms does not need treatment.
A negative result can give false reassurance if the symptoms are caused by an allergen that is not in the mix.

Get tested