Understanding Dog Allergens: A Scientific Overview

Dogs are beloved companions for many, but for millions worldwide, they can also be a significant source of allergies. Dog allergies are primarily driven by a group of proteins in the animal's skin, saliva, and urine, most notably Can f 1 and Can f 2. In order to improve the quality of life of dog allergy sufferers, it’s crucial to understand the biological properties of these allergens and their management strategies. Let’s dive in!

What Causes Dog Allergies?

Canine allergies are not triggered by a dog's hair itself, as commonly believed, but rather by proteins secreted by the animal. These proteins adhere to fur and dander, tiny flakes of skin, which then become airborne or settle on surfaces. Upon inhalation or contact, sensitized individuals may develop symptoms such as sneezing, nasal congestion, wheezing, coughing, itchy eyes, and even asthma.

Major Dog Allergens Identified

Several dog allergens have been characterized, including:

• Can f 1: The primary dog allergen is a lipocalin protein. It is produced in the tongue epithelial tissue and found in saliva and dander.
• Can f 2: The secondary dog allergen is a lipocalin structurally similar to Can f 1, but relatively less prevalent.
• Can f 3: A serum albumin present in dog blood and saliva. Due to its structural similarity to albumins from other animals, it can lead to cross-reactivity with other species (e.g., cats, horses).
• Can f 4: Another lipocalin associated with dog hair and dander. Not very prevalent
• Can f 5: A prostatic kallikrein found specifically in the urine of male dogs, potentially causing gender-specific allergenicity.

Other minor allergens include Can f 6, a lipocalin closely related to major cat allergens like Fel d 4, highlighting the complexity and cross-reactivity of pet allergies.

Sensitization and Clinical Implications

Sensitization to dog allergens is a significant risk factor for the development of allergic rhinitis and asthma. Exposure to dog allergens has been strongly linked to asthma severity, particularly among inner-city children. Interestingly, sensitization patterns vary geographically and individually. Some individuals may only react to certain proteins like Can f 1 or Can f 5, while others may react to multiple components, complicating diagnosis and management. Most sensitized individuals are allergic to Can f 1 and Can f 2.

Cross-Reactivity and Its Challenges

Cross-reactivity between dog allergens and those from other animals can complicate clinical allergy testing and interpretation. For example, individuals allergic to cat albumin (Fel d 2) may also react to dog albumin (Can f 3) due to the high degree of protein homology. Moreover, sensitization to lipocalins, a common allergen family across species, means that allergic individuals might experience symptoms around a variety of animals, including cats, horses, and rodents.

Dog Allergens persist in the environment

Like Fel d 1 in cats, dog allergens are lightweight and adhesive. Can f 1, in particular, can remain airborne for long periods and persist in homes even after the dog has been removed. Studies have detected dog allergens in places without resident dogs, such as offices, schools, and in public transport. There have been largely unsuccessful efforts to create hypoallergenic dog breeds. If interested, you can read more about:

1. Non-shedding dogs
2. Small dogs:
   1. Small dogs that don’t shed
   2. Small hypoallergenic dogs
3. Large dogs:
   1. Large dogs that don’t shed
   2. Large hypoallergenic dogs

It is important to note that research shows that all dogs produce allergens, though levels may vary among individual animals rather than breeds.

Managing dog allergies

In light of the emotional bond between humans and their canine companions, most individuals seek strategies to manage symptoms without rehoming their pet. Some effective strategies include:

1. Environmental Controls:
   1. Routine vacuuming with HEPA filters.
   2. Using high-efficiency HEPA purifiers for particulate air.
   3. Washing dog bedding and grooming pets frequently to reduce dander.
   4. Creating pet-free zones in the bedrooms.
2. Medical Treatments:
   1. It is possible to use antihistamines, corticosteroids, and leukotriene receptor antagonists to help manage allergic symptoms.
   2. Allergen-specific immunotherapy, allergy shots targeting can f allergens have been shown to be effective in many cases.
3. Medical Therapies:
   1. Sublingual immunotherapy (SLIT) is under investigation for dog allergens offering a less invasive alternative to traditional injections in dogs.
   2. IgE-targeting monoclonal antibodies such as omalizumab (an asthma drug) have also shown benefits for severe cases.
4. Biotech Innovations
   Emerging biotechnologies have introduced novel approaches for allergen control. One such product is the Pacagen Dog Allergen Neutralizing Spray, which employs a special protein derived from alpacas to deactivate Can f 1 and Can f 2 in the home. This represents a targeted strategy to eliminate dog allergens directly at its source.

Read more about the four pillars of allergen protection here.

Future Directions in Dog Allergy Research

Advances in molecular allergy are improving our ability to diagnose specific allergy sensitizations. Component-resolved diagnostics (CRD) allow for the identification of sensitization to individual dog allergens like Can f 1 or Can f 5, leading to more personalized treatment plans. Editing of genes and biotechnological interventions aimed at reducing allergen production in animals are still in very early stages but hold promise. Additionally, understanding how early life exposure to dogs influences allergy development is an active area of research. Some studies suggest that exposure during infancy might promote immune tolerance, while others indicate an increased risk, depending on specific genetic and environmental factors.

Overall, complete avoidance of dog allergen exposure is difficult, especially given the pervasive nature of these allergens, however, targeted environmental control measures, medical therapies, and emerging strategies offer multiple pathways to peaceful, easy coexistence.

References:

• Platts-Mills, Thomas A.E. The role of indoor allergens in chronic allergic disease. Journal of Allergy and Clinical Immunology, Volume 119, Issue 2, 297 - 302
• Vredegoor, Doris W. et al. Can f 1 levels in hair and homes of different dog breeds: Lack of evidence to describe any dog breed as hypoallergenic. Journal of Allergy and Clinical Immunology, Volume 130, Issue 4, 904 - 909.e7
• Salo, Päivi M. et al. Exposure to multiple indoor allergens in US homes and its relationship to asthma. Journal of Allergy and Clinical Immunology, Volume 121, Issue 3, 678 - 684.e2
• Liccardi, G; Passalacqua, G; et al. Is Sensitization to Furry Animals an Independent Allergic Phenotype in Nonoccupationally Exposed Individuals? J Investig Allergol Clin Immunol 2011; Vol. 21(2), 137-141
• Nicholas CE, Wegienka GR, Havstad SL, Zoratti EM, Ownby DR, Johnson CC. Dog Allergen Levels in Homes with Hypoallergenic Compared with Nonhypoallergenic Dogs. American Journal of Rhinology & Allergy. 2011;25(4):252-256. doi:10.2500/ajra.2011.25.3606
• Basagaña M, Luengo O, Labrador M, Garriga T, Mattsson L, Lidholm J, Cardona V. Component-Resolved Diagnosis of Dog Allergy. J Investig Allergol Clin Immunol 2017; Vol 27(3) : 185-187. doi: 10.18176/jiaci.0150
• Ownby DR, Johnson CC, Peterson EL. Exposure to Dogs and Cats in the First Year of Life and Risk of Allergic Sensitization at 6 to 7 Years of Age. JAMA. 2002;288(8):963–972. doi:10.1001/jama.288.8.963