Clinical Information

Dog (canine) dander allergy is one of the most common epidermal allergies in the United States, with an estimated prevalence of sensitization of approximately 10%. Overall, allergies to dogs and cats may afflict up to 20% of the world’s population, and the prevalence appears to be increasing over time. The assessment of dog allergen-related sensitivity and allergy is dependent upon the presence of compatible clinical symptoms in the context of exposure, with support from identification of potential canine-specific IgE allergen antibodies either by skin testing or in vitro serology testing.

There is a correlation between elevated total dog (canine) IgE allergen antibodies and an increased likelihood of a clinical allergic response. Once an elevated antibody response to total dog dander IgE extract is established, assessment for the presence of specific IgE antibodies to the most common dog allergenic components will be performed, which can yield additional, potentially useful information for clinical assessment of dog allergy and sensitization. During dog component allergen IgE antibody testing, the presence of IgE antibodies specific for potentially allergenic individual proteins, namely Can f 1, Can f 2, Can f 3, Can f 4, Can f 5, and Can f 6, are individually assessed. The determination of the relative amount of IgE antibody to specific dog components can aid in assessment of the potential strength and type of allergenic response. However, the correlation between total serum IgE testing and skin testing is not ideal, with estimates of 52% concordance. In vitro testing has generally focused on assessing for the presence of total IgE serum antibodies to total dog allergen extracts and has overall estimated sensitivities of 75% in symptomatic individuals.

Canis familiaris allergen 1 (Can f 1) is a major allergen and is a salivary lipocalin protein found in all homes with dogs. Particles containing Can f 1 can remain airborne and can be inhaled. Several studies have demonstrated that approximately half of the individuals with dog allergies have IgE antibodies directed exclusively to the Can f 1 component. Increasing IgE antibody concentrations against lipocalins, such as Can f 1, correlates with the severity of asthma. Sensitization to Can f 1 in childhood was significantly associated with symptoms to dog allergy at age 16 years, and high levels of antibodies to Can f 1 were strongly associated with asthma in a population-based study of 19 year olds. Can f 1 is the most dominant dog allergen, although only 64% of individuals who are allergic to dogs react to Can f 1. While Can f 1 can be reliably used to identify dog-allergic individuals who sensitized to Can f 1, sensitivity for detecting potential dog allergy (and allergen sensitization) increases if multiple allergen components are assayed.

Can f 2 is a salivary lipocalin protein and an allergen present in dog hair and dander. Sensitivity to Can f 2 is associated with high levels of bronchial inflammation and is more common among patients with severe asthma. It is believed that sensitized patients with reactivity to Can f 2 will always react to Can f 1.

Can f 3 is a serum albumin allergen found in dog dander, hair, epithelia, saliva, and in house dust and is considered an intermediate dog allergy component. Sensitization to Can f 3 is associated with increased risks of current asthma, current allergic rhinitis, and concomitant asthma and allergic rhinitis.(1) There is observed cross-reactivity of Can f 3 patient IgE antibodies with albumins from many species, including the cat allergen Fel d 2, which may cause sensitization.

Can f 4 is the most abundantly detected allergen in dog fur and a major allergen component of dog hair and dander extracts. Sensitization to the lipocalin Can f 4 is associated with asthma and serves as a marker for clinically relevant dog allergy. Assessment of antibodies to Can f 4, in combination with other dog allergens, may improve the reliability of dog allergy assessment.

Can f 5 is a prostatic kallikrein component of dog hair and dander produced by intact (unneutered) male dogs. Approximately two-thirds of individuals who are allergic to canines demonstrate IgE reactivity to Can f 5. Additionally, a substantial proportion of those individuals are monosensitized to Can f 5 and react specifically to intact male dogs rather than female dogs or castrated male dogs. Sensitization to Can f 5 is associated with asthma and rhinoconjunctivitis symptoms and can contribute to polysensitization in individuals with IgE responses to multiple animal allergen molecules. Due to cross-reactivity with prostate-specific antigen of human seminal plasma, sensitization to Can f 5 may also contribute to the occurrence of human sexual disorders, including infertility.

Can f 6 is a major dog allergen present in dog dander. Sensitization to Can f 6 is associated with dog-related rhinitis and asthma. Can f 6 shares extensive cross-reactivity with other mammalian lipocalins, particularly cat and horse, and thus contributes to multi-animal allergic sensitization and potential resulting clinical respiratory symptoms.

Polysensitization to multiple allergens should be considered during the evaluation of dog component assay results. In a study of 75 patients with clinical allergy, the majority exhibited IgE antibodies reactive with Can f 1 and Can f 2. Asthma and decreased lung function were most strongly associated with sensitization to a group of 27 components, including Can f 1, Can f 2, and Can f 3. Polysensitization to 3 or more allergen molecules from dogs was a better predictor of dog allergy-related symptoms than results of IgE antibody tests utilizing total dog allergen extracts. Most dog-sensitized children are reactive to more than one dog allergen component, with co-sensitization to Can f 5 and Can f 1/Can f 2 conferring higher asthma risks. Reducing canine exposure should be considered if co-reactivity to these components is present.

Table. Specific Dog Allergens