Scrutinizing the science behind allergy- reducing cat food

Domestic cats (Felis catus) are the source of the third most common respiratory allergen, just behind pollen and house dust mites. With pet ownership increasing during the pandemic and many people spending 90% of their time indoors, the incidence of cat allergies is expected to increase in the coming years. So what can be done to make life more comfortable for people who are allergic?

The most common cat allergen

The World Health Organization currently recognizes eight cat allergens, with the most prominent one being Fel d1. This protein is shed by cats and can cause an allergic response in up to 96% of people with cat allergies. Fel d1 is primarily secreted from the cat’s salivary and sebaceous glands as a small secretoglobin protein. Although the concentration of Fel d1 can vary based on a cat’s age, breed and sex, every cat produces this allergen, including ‘hypoallergenic’ breeds.

The exact function of Fel d1 remains largely unknown. However, studies have shown that neutered cats express lower concentrations of Fel d1. This suggests a potential role as a carrier molecule for steroids, hormones and pheromones.

Fel d1 in the environment

As cats groom themselves, their saliva spreads across their fur and skin. This combination of dried skin, hair and saliva forms a Fel d1 reservoir that sheds into the environment as ‘dander’.

Dander comes in various shapes and sizes. An article published in the Journal of Feline Medicine and Surgery found that 23% of cat dander was smaller than 4.5 μm. This allows Fel d1 to remain airborne for several days before settling in dust, sticking to clothing or reaching small respiratory pathways deep within the lungs.

Significant levels of Fel d1 have even been found in places without any cats at all, such as schools, hospitals and practically every public building. With not only cat owners but also the general public at risk, the veterinary community is urged to explore new methods to limit the spread of Fel d1.

Neutralizing Fel d1 using diet

To help protect people affected by cat allergies, researchers have developed a method to neutralize Fel d1 and prevent environmental contamination. This approach introduces chickens to Fel d1 and utilizes their immune system to produce anti-Fel d1 antibodies in freshly laid eggs. These antibodies are then extracted from the egg yolk, purified and coated onto kibble. As a cat eats the antibody-coated kibble, some of the active Fel d1 in the saliva will become neutralized. This reduces the spread of active allergen, while the remainder of the neutralizing antibody makes its way through the cat’s digestive system. At a molecular level, these neutralizing antibodies bind to Fel d1 and cover the IgE binding sites known to stimulate an allergic response in humans.

So far, Purina is the first and only company to bring this technology to market. It has released some interesting data:

Cat’s saliva
In a 6-week pilot study funded by Purina, cats fed anti-Fel d1 kibble (test diet) showed a 30% decrease in active Fel d1 proteins in salivary samples after 2 weeks of receiving the test diet. A subsequent study in 20 domestic shorthair cats found >80% of the cats showed a ≥20%reduction in active salivary Fel d1. This supports the potential of this diet to decrease active Fel d1 levels across different patients.

Cat’s skin
Hair samples taken from 105 cats fed the test diet over 12 weeks revealed a mean 47% reduction in active Fel d1. It is yet to be determined whether this decrease was caused by dispersion of neutralizing antibodies through saliva and grooming, or if there are other mechanisms involved that directly neutralize cutaneous-Fel d1.

Effective for treating cat allergies?

To assess the efficacy of anti-Fel d1 diets in reducing symptoms of cat-related allergies, cat bedding
was removed after 4 weeks of feeding the test diet and used to provoke allergies in 11 cat-sensitive individuals. Interestingly, the results suggested clinical improvements as both nasal symptoms and ocular scores improved across individuals.

Role of veterinarians

Veterinarians are in a unique position to help allergic pet owners, promote the welfare of cats and improve human healthcare standards by using innovations in diet to address common issues like cat allergies.