Humans and their pets: are allergies comparable?? The way humans live together. Animal has changed a lot in the last – few – decades. Housing conditions such as proximity, cleanliness, ambient air, exercise patterns, and diet/food affect human and animal health in many ways. They also influence the development and intensity of allergological and immunological diseases. Why should we care?
Humans and animals can suffer from the same allergies.
Underlying immune mechanisms are very similar among mammals, together with adapted living conditions, they allow transfer of knowledge about triggers, prevention, diagnosis and treatment between different species.
This sharing of human and animal patients saves time, money and subjects in the development of new diagnostics and therapeutics and also allows a reduction in animal testing with artificial animal models.
Since lifestyle factors have become very similar in humans and animals, it makes sense to look for allergy triggers in different species at the same time. Consequently, within the framework of comparative medicine, the knowledge of prevention and treatment of allergies of one species can also be applied to the advantage of another one.
The IgE antibody as a significant factor within a type I allergic reaction is found in all mammals. All mammals, primates and thus a large part of our domestic and also farm animals can therefore suffer from allergic diseases (Fig. 1).
Fig. The genetic predisposition to asthma. Allergy is called atopy in humans (fig. 2). It is also found in dogs and horses, in other species there are rather differences regarding the breed. Among dogs, especially Labradors, Golden Retrievers, Setters, Terriers, West Highland White Terriers, Bulldogs, Boxers and Cocker Spaniels often suffer from allergies. In cats, the Abyssinian cat and the Devon cat, and in horses, the Danish Warmblood, Morgan, Swedish Warmblood, and Oldenburg lead the list of breeds susceptible to allergies. Farm animals also produce IgE, so sheep, goats, pigs and cattle are also capable of anaphylactic shock (excellently summarized in the review by Gershwin L). 3 In cattle, IgE correlates particularly with parasite infestation, whereas type I allergies are very rarely observed in cattle, although specific IgE against inhaled allergens have also been found. Allergic reactions have even been observed in birds, but the pathomechanisms and antibodies responsible are not fully understood.
Fig. 2: The genetic predisposition in humans is reflected in the numbers of allergic diseases in high-risk children (first-degree family members have allergy). Sources: Litonjua AA 1 , Ghazali RB 2
Similar – but not the same – symptoms
The well-known allergic symptoms of humans – rhinoconjunctivitis, atopic dermatitis, angioedema, but also asthmatic symptoms up to life-threatening anaphylactic shock – can also be found in animals. However, mainly cats and horses suffer from asthmatic complaints, while these are hardly observed in dogs. It is also known from cattle that they do not suffer from asthma. In man's best friend, the dog, primarily skin problems are observed, such as itching, redness, loss of fur. Atopic dermatitis also exists in cats and horses. All of them also share the risk of anaphylactic shock.
Diagnosis – the same methods can be used
As in humans, our animals can be tested for specific IgE antibodies in the serum. The two hurdles to overcome here are A) the fact that animals, especially those with close proximity to soil and high propensity for parasite infestation, also have high background IgE levels, these can roll over or mask a specific response in RAST or ELISA and result in a high background signal; and B) the fact that the method of molecular allergy diagnostics already available in clinical practice for human patients is not yet optimized for animal patients- information about relevant allergen sources and the allergen molecules contained therein is often missing. For humans, there are already several micro- and macro-array chips for this purpose. This precise diagnostic procedure ultimately also allows optimal management and an adapted, individualized therapy of the allergy. This would also be conceivable in animals.
Treatment – where humans could learn from animal patients
The first step in the management of allergies, both in human and veterinary medicine, is allergen avoidance. Less antihistamines are used to treat the symptoms in animals than in humans, with priority being given to z.B. in dogs rather a symptomatic treatment especially of itching and possibly of flea infestation. However, immunotherapy (desensitization, hyposensitization) is already successfully used in cats, dogs and horses. The newer forms of treatment with so-called biologics against IL-31 and IL-5 were even first used in animals (horse, dog) 4 and are now also used in humans.
Factors influencing the development of allergies – the same in humans and animals
Many factors can influence the development of allergy and asthma. In the concept of One Health, lifestyle factors, environmental influences and climatic changes are also particularly relevant here. All of these affect our pets and farm animals as well. This refers to urban living conditions with heavy sealing and resulting low biodiversity of plants, animal species, natural soil/earth. 5 The lack of contact with nature and green space 6 as well as with rural living conditions such as farms and forests is reflected in higher allergy prevalence in humans and animals. The – mostly negative – development of nutrition and food (highly processed, high-calorie, low-fiber diets) additionally results in an impoverished or altered intestinal microbiome (dysbiosis). Also the microbiome of the skin, which is even exchanged between owner and dog, is easily influenced, z.B. through frequent washing, contact with surfactants, detergents and fragrances. Dogs and masters also often suffer from allergies together. 7 Since there is obviously a great similarity between humans and other mammals in allergic and asthmatic diseases, a comparison for mutual benefit seems indeed justified. In the EAACI working group "Comparative Allergology", therefore, the comparison between allergological and immunological diseases in humans and animals is systematically made in the form of different position papers and review articles. 8-12 On the one hand, triggers are determined, in order to be able to fix preventive measures with it. On the other hand, the optimization of diagnostics and treatment can also benefit from the comparison of different species, numerous drugs and test procedures could and could thus reach the clinic and the patient more quickly and efficiently.