Human allergy to cats: A review for veterinarians on prevalence, causes, symptoms and control

Practical relevance: Human allergy to cats affects a substantial and growing proportion of the global population, and cat allergy is regarded as the third most common cause of human respiratory allergies, and the second most common indoor cause. Veterinarians will frequently encounter owners who are cat-allergic, and having an understanding of this disease and the methods available to help control the allergy will assist them in giving appropriate advice, alongside human healthcare professionals. Aim: The aim of this review is to summarise currently available data on the prevalence, causes, symptoms and control of human allergy to cats. In terms of managing cat allergy, the emphasis is on reviewing current and emerging modalities to reduce environmental exposure to cat allergens rather than on pharmacotherapy or immunotherapy, as it is in these areas in particular that the veterinarian may be able to offer help and advice to complement that of human healthcare professionals. Evidence base: The information in this review is drawn from the current and historical literature on human allergy to cats, and approaches to reduce exposure to cat allergens and manage symptoms of cat allergy.

An Overview of the Relevance of IgG4 Antibodies in Allergic Disease with a Focus on Food Allergens

Antibodies of the IgG4 isotype are strongly associated with allergic disease but have several properties such as not precipitating with allergens, not activating complement and poor binding to Fcγ receptors that argue against a pro-inflammatory role. In keeping with that, IgG4 antibodies are a striking feature of the response to immunotherapy. In two naturally occurring situations IgG4 antibodies are common with low or absent IgE antibodies. The first example is children raised in a house with a cat and the second is eosinophilic esophagitis (EoE). In many population-based cohorts, the ownership of a cat in early childhood is associated with a decreased prevalence of a cat allergy at age 10. The second example (i.e., EoE) is a novel form of food allergy that is not mediated by IgE and is related to consuming cow’s milk or wheat. In EoE, patients have IgG4 to milk proteins in high > 10 µg/mL or very high > 100 µg/mL titers. Enigmatically these patients are found to have deposits of IgG4 in the wall of their inflamed esophagus. The factors that have given rise to EoE remain unclear; however, changes in food processing over the past 50 years, particularly ultra-heat treatment and the high pressure homogenization of milk, represent a logical hypothesis.

Unexpected Cat Allergy in Infants with Persistent Atopic Dermatitis

Atopic dermatitis is a chronic, recurrent inflammatory skin disease usually caused by genetic predisposition, immune dysregulation, epidermal barrier dysfunction and interaction of environmental factors. Atopic dermatitis is part of atopic march and is often accompanied by food allergy. Aeroallergenic sensitization at early age is not an expected finding. Here, we present five cases with moderate-severe atopic dermatitis during infancy, in whom food allergy was detected and the symptoms improved only partially despite elimination and treatment. Sensitization was investigated in patients with a history of intense exposure to cats by specific IgE and skin prick test in infants with atopic dermatitis who had food allergy and persistant findings. Egg allergy was detected in four of the cases, wheat allergy in one. Cat allergy was present in all. Elimination diet was started in all cases. When exposure to cats was reduced, a marked improvement in the findings of atopic dermatitis was observed in all cases. Allergic diseases are increasing day by day. Unexpected aeroallergenic sensitization is now more common in the early stages of life. Allergic patients, regardless of age, should be questioned in detail for aeroallergen exposure. If it is detected; necessary preventive measures should be taken.

Innovative Management Methods for Patients Allergic to Cats

The prevalence of allergies to domestic animals increases due to the increase in the number of pets worldwide, followed by serious medical and social problems. Domestic cat (Felis domesticus) is one of the most common pets and one of the most frequent (after dust mite) source of indoor allergens and risk factor for bronchial asthma and allergic rhinitis. This review collects relevant information on the issues of hypersensitivity to cat allergens (the term «cat allergy» will be used later). The authors consider issues of diagnosis, treatment and prevention of this condition. Special attention is given to the management of patients with cat allergies and particularly usage of special nutrition for cats that can reduce the level of the main cat allergen Fel d 1 in the environment. Whereas, this leads to decrease of allergic diseases symptoms severity.

Sensitization to cat and dog components and prediction of symptoms in cat-sensitized children.

Background: Sensitization to cat and/or dog allergens during childhood represents a risk factor for the development of allergic diseases later in life.Material and Methods: The study investigated the association of patterns of sensitization to cat and dog allergen components with clinical symptoms of allergy to these furry animals among cat-sensitized children. It included 50 children aged 5-17 years who showed sensitization to cat in the skin prick test. They were considered to have cat allergy if they suffered from one or more allergy symptoms when being exposed to contact with a cat. The children were evaluated for the presence of bronchial asthma, atopic dermatitis and allergic rhinitis. Their mothers completed a questionnaire on pet exposure at home. Levels of serum IgE cat epitopes Fel d (1, 2, 4), as well as dog components Can f (1, 2, 3, 5) were measured in all the studied children.Results: Respiratory symptoms following exposure to the cat allergen were most common in children with Fel d 2 epitope (p = 0.041). After contact with a dog, respiratory symptoms were most common in children with Can f 1 epitope (p = 0.042), eczema in children with sensitization to both Can f 1 (p = 0.009) and Can f 2 (p = 0.002), whereas eye symptoms occurred mostly in children with Can f 3 (p = 0.039).Conclusions: Molecular diagnosis in patients with pet allergy may help clinicians to predict clinical symptoms and their severity.

Immunization of Cats against Fel d 1 Results in Reduced Allergic Symptoms of Owners

An innovative approach was tested to treat cat allergy in humans by vaccinating cats with Fel-CuMV (HypoCatTM), a vaccine against the major cat allergen Fel d 1 based on virus-like particles derived from cucumber mosaic virus (CuMV-VLPs). Upon vaccination, cats develop neutralizing antibodies against the allergen Fel d 1, which reduces the level of reactive allergen, thus lowering the symptoms or even preventing allergic reactions in humans. The combined methodological field study included ten cat-allergic participants who lived together with their cats (n = 13), that were immunized with Fel-CuMV. The aim was to determine methods for measuring a change in allergic symptoms. A home-based provocation test (petting time and organ specific symptom score (OSSS)) and a general weekly (or monthly) symptom score (G(W)SS) were used to assess changes in allergic symptoms. The petting time until a pre-defined level of allergic symptoms was reached increased already early after vaccination of the cats and was apparent over the course of the study. In addition, the OSSS after provocation and G(W)SS recorded a persistent reduction in symptoms over the study period and could serve for long-term assessment. Hence, the immunization of cats with HypoCatTM (Fel-CuMV) may have a positive impact on the cat allergy of the owner, and changes could be assessed by the provocation test as well as G(W)SS.