26. April 2021
Dogs, cats and asthma – findings from molecular allergy diagnostics

Pets, especially dogs and cats, can cause allergies. But clearly no one is allergic to the entire dog – just to tiny molecules, for example, on the dog’s hair – and not always the hair of one’s own dog. So how can the source of the allergy be determined?

There is one method that can detect individual allergy-causing molecules: Molecular allergy diagnostics, or CRD (component-reactive diagnosis). Researchers in Denmark and Sweden investigated the advantages of the method for pet allergies by analysing studies published between 1997 and 2020.


What can be achieved with molecular allergy diagnostics?

The method can be used to find out whether the source of the allergy is really one’s own dog or in fact the neighbour’s cat. This cannot always be detected through the usual allergy tests.
If you know which individual substance (allergen) triggers the allergy, you can avoid the corresponding allergen or pet (or its owner). What’s more, patients can be offered individual treatment for this single allergen. The probability that the treatment will be effective is assumed to be higher.


What did the study reveal?


Finding: male dog allergen

In dogs, six out of seven known single allergens are available for molecular allergy testing. The researchers reported that more than half of the people tested for allergies reacted to only one specific allergen. This allergen, Can f 5, is only produced by male dogs. A standard skin prick test using extract from female dogs did not trigger any allergic reactions. This means that these people cannot keep a male dog as a pet, but they can keep a female dog.


Finding: allergens and increased risk of asthma

Four of the eight known cat allergen molecules can be found using the molecular allergy test. Two of them – Fel d 1 and Fel d 4 – are associated with an increased risk of asthma in children. A link between certain dog allergen molecules and asthma was also revealed.
These findings may make it possible to better predict asthmatic diseases. Children who are especially sensitive to these allergens also have a higher risk of developing asthma later in life.


How do molecular allergy diagnostics work?

Various molecules are responsible for an allergic reaction. Most of them are protein molecules (proteins). If the human immune system comes into contact with one of these allergy triggers, it creates antibodies. These antibodies are made for precisely this one allergy trigger. They are called type E immunoglobulins (IgE). IgE are found in the blood of people with allergies.


This also means that they can be detected in a blood sample. With modern laboratory technology, it is even possible to analyse exactly which allergen molecule individual IgE groups are targeting. For example, there are seven known dog allergen molecules, and eight for cats. Not all of these allergens are individually available yet for molecular allergy diagnostics. However, the method is already much more accurate than the standard allergy tests.



Individual allergen molecules can be detected with molecular allergy diagnostics. This is important in order to be able to clearly categorise the allergies. With this knowledge, individual treatment can be prescribed, or the allergens can be avoided more easily.



Schoos AM. Component-resolved diagnostics in pet allergy: Current perspectives and future directions. J Allergy Clin Immunol. 2021 Jan 11:S0091-6749(21)00003-8.