Dog allergy. To have a pet or not to have one?
The answer to this question would be ‘’it depends’’! It depends on what proteins in the dog you are allergic to. There are proteins that are only found in dogs. In this situation, having another furry animal is possible. It is different if you are allergic to dog proteins, to which similar molecules are found in cats, horses, rabbits, or guinea pigs.
But there is a canine protein that is only found in the urine of male dogs, which means it is possible to have a female dog without allergy symptoms.
Therefore, if you react with hypersensitivity to contact with your dog, it is best to find out which proteins are sensitising you. You can test for this with molecular diagnostics. These are tests that determine antibodies E (IgE) in blood serum to individual dog allergen proteins and are available from many laboratories.
Diagnosis of dog allergy
The most common diagnosis of dog allergy is based on spot skin testing. An animal allergen, which is a mixture of all sensitising and non-sensitising proteins, is applied to the skin. The skin is then punctured at the spot where the allergen drop is applied. This procedure ensures that the allergen is presented to the body’s immune cells.
The appearance of an appropriately sized bump on the skin indicates an allergy, but is it always to a dog? Not always!
Contamination of available dog allergen preparations for skin testing with major house dust mite allergens (Der p 1 and Der p 2) has been demonstrated. This can result in false positive reactions on skin prick tests with dog fur in patients allergic to house dust mites. 
Furthermore, even in a situation of dog allergy confirmed by skin tests, we cannot predict the consequences and give appropriate recommendations. Currently (January 2022), we know eight different canine allergen proteins. We can routinely determine 7 of them.
Dog allergy, and… milk allergy
A patient with a dog allergy may be allergic to one or more dog proteins. Rarely to all of them at the same time. Therefore, the allergy symptoms of each dog allergy patient may be slightly different.
Example: A result obtained in skin or blood tests based only on canine allergen extract can be positive for an allergy to…cow’s milk!
This occurs in patients allergic to Can f 3 dog protein, which belongs to a group of proteins called serum albumin. It has been shown that the first contact with a protein from the serum albumin group was through the ingestion of cow’s milk. Allergies to canine serum albumin can develop even without direct contact with this animal. Serum albumin is an important allergen involved in allergies to milk, meat and fur animals. Therefore, patients with an allergy to this protein may experience symptoms as a result of cross-reactions after drinking cow’s milk. A similar reaction may occur after contact with raw meat and fur animals .
Molecular diagnosis of allergy has the advantage over skin testing in that it allows us to assess against specific purified proteins without affecting the outcome of other allergens. And knowing the allergenic molecule allows us to make more targeted recommendations and prescriptions.
Dog allergens – Can f 1 and Can f 2
So what specifically sensitises us in a dog and what consequences this may have for us:
– Can f 1 (lipocalin) is an allergen produced by the salivary glands of the dog. It is also found in the fur (due to the dog licking itself). If you are allergic to it, you may be diagnosed with a primary allergy to dogs. In people with a dog allergy, Can f 1 is usually positive. Studies show that up to 90% of people with a dog allergy have E (IgE) antibodies to this very molecule. For this reason, it is called the main dog allergen. The route of exposure to this allergen is inhalation. It is therefore enough to breathe air in which dust floats, which may include exfoliated epidermis or hair residues. It can cause upper and lower respiratory tract symptoms . Homes where dogs are kept exclusively indoors have been shown to have elevated levels of Can f 1 compared to homes where dogs are kept outside most of the time. Furthermore, even in homes without dogs, there are detectable amounts of Can f 1 in dust samples. Bathing dogs reduces the overall amount of ‘free’ hair and may reduce Can f 1. However, having to repeatedly wash a dog can be difficult to maintain and unsuitable for the animal itself .
A good effect of canine allergen immunotherapy is expected in patients with Can f 1 allergy .
– Can f 2 (lipocalin) is found in dog saliva and hair. It sensitises about 35% of people with a dog allergy and enters the human body by inhalation . Furthermore, it usually accompanies a positive Can f 1 result, but the appearance of E antibodies to Can f 2 is associated with more severe asthma symptoms. Therefore, Can f 2 is considered a marker of asthma severity. Hypersensitivity to Can f 2 often occurs with this condition .
A good effect of canine allergen immunotherapy is expected in patients with Can f 2 allergy .
Can f 5 – only in males
- – Can f 5 (calicrein) is the main canine allergen sensitising up to 71% of people with dog allergy. Allergic individuals may experience upper and/or lower respiratory system symptoms . It is detected in the urine and hair of adult dogs – MALE DOGS!!! Therefore, in the case of sensitisation to only Can f 5 of the dog allergens, symptoms may only appear after contact with male animals. It has been proven that castration drastically reduces the concentration of Can f 5 in the urine and hair of the dog . Can f 5 has a similar structure to human prostate secreted protein (PSA) – which may explain the occurrence of IgE-mediated reactions in some women with dog allergy after contact with semen during sexual intercourse. It has been speculated that, in a group of women with Can f 5 allergy, difficulties with pregnancy may be due to sensitisation to this molecule [4, 11].
Other canine allergens
- Can f 3 is an inhalant allergen and belongs to a family of proteins called serum albumin. It sensitises almost half of people with dog allergy. It is found in the blood serum, hair, and hair and skin of dogs, while it is produced in the salivary glands and liver. It is responsible for cross-reactions with meat and animal products from various animals, including beef (and cow’s milk), lamb, game, and pork. It is a heat-sensitive protein, so consumption of heat-treated milk or meat should not cause allergic symptoms .
- Can f 4 (lipocalin) sensitises between 35 and 59% of canine allergy sufferers. This protein is detectable in dog saliva and is also temperature sensitive . It is the most abundant protein in dog allergy, which is often not reflected in skin test preparations or serum E antibody determinations. This is because the manufacturing process of such preparations can alter their allergenic activity. Thus, patients allergic to Can f 4 may be undiagnosed . The chosen preparation method means that different methods and allergen preparations may give divergent results on the prevalence of allergic sensitisation to Can f 4 canine. Therefore, the assumed number of people with allergy to this protein may be underestimated . Can f 4 is a marker for symptomatic canine allergy, as studies have shown that these antibodies were present in canine-allergic individuals diagnosed with allergic rhinitis or asthma .
- Can f 6 (lipocalin) present in saliva and exfoliated epidermis, sensitises approximately 38% of patients. It can cause cross-reactions with horse and cat hair. Can f 6, like Can f 4, is a marker for symptomatic dog allergy and may be missing from standard tests for diagnosing dog allergy [7, 9].
- Can f Fel d 1 like – belongs to the Fel d 1- related family of proteins, the main representative of which is Fel d 1, the main cat allergen. Sensitisation to it can cause cross-reactions between these animals.
translation: Julia Majsiak