Explanation

Rodent mix (allergy): what is measured?

The test measures, in one go, IgE antibodies against a fixed mix of allergens from 5 small mammals: guinea pig, rabbit, hamster, rat and mouse. For guinea pig, rabbit and hamster it concerns dander; for rat and mouse the mix also contains proteins from urine and blood, because these animals spread a large part of their allergens through their urine. The rabbit is biologically not a rodent, but is included in this mix. 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 animals are tested together, the result gives one number and a verdict of positive or negative, but not which animal the antibodies are directed against.

What can it detect?

Sensitization to at least one of the 5 animals in the mix: the body has made IgE antibodies against allergens from one or more of them
An indication of whether symptoms when caring for or working with rodents or rabbits may have an allergic cause

Result

What does the result mean?

Positive result

A positive result means that you have IgE antibodies against allergens from at least one of the animals in the mix: sensitization. That is not the same as an allergy, and the test does not say which animal the antibodies are directed against. In people who get symptoms when caring for a guinea pig, rabbit or hamster, or when working with rats or mice, for example in a laboratory or pet shop, a positive result fits an allergy to these animals. Symptoms that fit are sneezing, a blocked or runny nose, itchy or watery eyes, a skin rash or shortness of breath. 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 the 5 animals were found. An IgE-mediated allergy to these animals is then much less likely. An allergy to animals that are not in the mix, such as cat, dog, horse, gerbil, chinchilla or birds, is missed. Symptoms when caring for animals can also come from house dust mite, from molds in hay or bedding, or from irritants such as dust and odors.

After an abnormal result

The GP mainly looks at the history: with which animal and in which situation the symptoms occur, and if needed a test for single animals follows to determine which animal it is. With an allergy, the main advice is to limit contact with that animal; with symptoms from work, the occupational physician can help look at measures at work. With symptoms that are not controlled with medication or with asthma, referral to a 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. With these animals the history is often clear, because the symptoms occur on contact with a certain animal or during work. The mix is mainly a first step: a negative result makes an allergy to these animals less likely, a positive result can be looked into further with a test for single animals.

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 animal you react to; that requires a test for single animals.
Cat, dog, horse, birds and other small pets such as gerbil and chinchilla 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 that occur on contact with guinea pigs, rabbits, hamsters, rats or mice: at home with a pet, or during work in a laboratory, pet shop, veterinary practice or petting farm. If it is clear which animal is involved, a test for that single animal 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?

Allergy to rodents and rabbits occurs in people who keep these animals as pets, and more often in people who work with them, such as with laboratory animals. The Dutch medical specialists' guideline (FMS) on work-related asthma names animal proteins among the allergens that can cause asthma from work. Sensitization is more common than the allergy itself.

FMS guideline on work-related asthma; no Dutch prevalence figure has been checked

Drawbacks and risks

A positive result without symptoms can lead to unnecessarily giving away a pet, while sensitization without symptoms does not need treatment.
A negative result can give false reassurance if the symptoms are caused by an animal that is not in the mix.

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