Component-based diagnosis in pet allergy improves treatment plans

Key takeaways:

• Diagnostics can identify sensitization to Can F 1, Fel D 1, and other components.
• Interventions begin with minimizing exposure.
• Inhaled corticosteroids, immunotherapy and biologics may follow.

Precise diagnoses that target specific dog and cat allergens can improve treatment and enable people with pet allergies to spend long, happy lives together with their furry family members, Gary Falcetano, PA, told Healio.

“Improved diagnostics have really improved satisfaction among patients,” said Falcetano, U.S. scientific affairs manager at Thermo Fisher Scientific. “They have better insight into their disease.”

Diagnostic value

These diagnoses are possible despite the range of symptoms that these allergies involve, Falcetano said, with prevalence impacting between 10% and 20% of the population.

Gary Falcetano

“Most pet allergies present as respiratory related,” Falcetano said. “Anything from upper airway symptoms like rhinitis or even rhinoconjunctivitis to lower airway symptoms like asthma.”

Treatment begins with determining whether patients even have a pet allergy at all, as they often have symptoms without knowing their cause.

“Where it starts is actually getting the diagnosis right,” Falcetano said. “A dog can be outside during pollen season and bringing in a bunch of pollen on their fur. You have contact with the dog and you have symptoms, and you think it’s the dog.”

Clinicians should begin with the patient’s history and delve into when symptoms began.

“Do you have them every time you’re exposed to a dog? Do you have them with every dog you’re exposed to, or just certain dogs?” Falcetano said. “Getting that right has always been a challenge.”

Clinicians can proceed with in vivo skin prick testing or in vitro serological (blood) testing using whole dog or cat extracts or specific proteins such as Can f 1 for dogs and Fel d 1 for cats.

“We have been able to be more precise in a lot of our different food diagnoses by looking at individual allergen components, usually proteins,” Falcetano said. “The same is true with pets.”

More precise diagnosis takes a deeper dive to see which components patients are sensitized to, he explained.

“By knowing the characteristics of each of those components, we can better predict how a patient might express their disease and then also better predict how to manage that disease based on what we’re seeing,” he said.

Alternatives to treatment

Once a diagnosis has been found, interventions might not need to include medication, Falcetano said.

“It’s ideal not to have any type of pharmaceutical intervention. So that’s why the exposure reduction techniques are so important first, because they can obviously limit the need for pharmaceutical interventions,” he said. “And even if you do need them, though, they may limit the amount of medication you need to actually get relief from your symptoms.”

For example, he said, most patients with cat allergy are sensitized to Fel d 1. Purina’s Live Clear cat food reduces the amount of Fel d 1 that cats express.

“It binds with the Fel d 1 in their saliva, tends to reduce their expression of Fel d 1, consequently causing less symptoms in humans,” Falcetano said.

One of the simplest and most effective steps is just keeping the pet out of the bedroom, he also suggested, especially when children have the allergy.

“They spend 9, 10, 11 hours a day in that space,” he said. “If we can protect that space, it can have a dramatic impact on their symptoms.”

Bathing pets once or twice a week, “which is always fun with cats,” Falcetano said, can reduce the amount of allergens they release into the environment too.

Thermo Fisher also provides other expert advice as part of its Allergy Insider program, including cleaning tips, vacuums and air purifiers with HEPA filters, and litter box placement.

Falcetano additionally noted that no cats or dogs are completely free of allergens, even those that do not have any fur, despite marketing that claims otherwise.

“Those allergens are expressed in their saliva, in their urine,” he said. “It really doesn’t matter whether they have a big furry coat or not.”

But patients can be selective in the pets they adopt.

“Certain breeds will express less allergen,” he said. “Some people will have less symptoms with them.”

Some patients may do better with female dogs as well, he continued, as male dogs produce an allergen component called Can f 5 in their prostate. Between 30% and 58% of patients sensitized to dog may be mono-sensitized to Can f 5, which means they may be able to tolerate a female dog.

“That’s really interesting, to allow us to target our management and even our advice to patients on whether they’re getting a dog based upon the sensitization profile,” Falcetano said.

Pharmaceutical treatment

Medication is available for patients with pet allergies.

“People like to go to a pill first for an intervention,” Falcetano said.

However, inhaled nasal corticosteroids are the preferred treatment for patients with pet allergies who experience symptoms despite nonpharmaceutical strategies, he said.

“Most people will actually go to a nonsedating antihistamine first,” Falcetano said. “But really, the goal, the gold standard treatment first, should be an inhaled nasal steroid.”

Falcetano also advised that first-generation antihistamines such as diphenhydramine products have been supplanted by the newer second-generation non-sedating antihistamines.

“We have such good nonsedating antihistamines, second-generation antihistamines, that most allergists, most clinicians in general, will try to steer you away from those first-generation antihistamines,” he said.

With very little systemic absorption, he continued, nasal corticosteroids or a combination of inhaled nasal steroids and inhaled antihistamines are very safe and relatively free of side effects. But if exposure reduction and initial therapeutics are not successful or satisfactory, immunotherapy is the next option.

“You don’t see immediate relief,” Falcetano said. “It also takes 3 to 5 years to get to a maintenance phase, so it is a bit of a commitment. But especially for people that have a more severe phenotype of disease and who are unwilling to completely get rid of their exposure, it’s a very good option.”

Immunotherapy for pet allergies has improved, Falcetano said, specifically targeting Can f 1 and Fel d 1 instead of whole extract. Research also is investigating individual molecules with a goal of immunotherapy designed around them, he continued, but these solutions may take some time to hit the market.

“That’s a long road just because of the FDA hurdles and the approval hurdles,” he said.

Biologic therapy including medication that targets IgE, IL-5 and IL-13 for patients with severe asthma may play a role in treating pet allergy as well, Falcetano said.

Treatment plans

Specific diagnoses based on individual allergen components will help clinicians decide which treatment is best for each patient, he said, adding that clinicians have been able to predict reaction severity in food allergy based on allergen components.

“Now with pet components and pet allergy, we can actually predict risk of having a more severe phenotype of disease,” Falcetano said.

Previous research has found that patients who are sensitized to a greater number of components are more likely to have more severe phenotypes of disease, he said.

“What does that mean for patients and clinicians? It allows us to now get better advice,” Falcetano said. “There might be that patient that needs to rehome [their pet], or that patient that needs convincing to go to immunotherapy.”

Being able to assess each patient’s risk can go a long way in helping them manage their disease more precisely and in a more personalized way, Falcetano continued.

These kinds of assessments are particularly important for children, he said, with studies indicating that early sensitization to multiple pet allergen components could lead to clinical disease during adolescence.

“You have to be able to give that insight that we really need to take this pet allergy seriously, because you could be on a trajectory to go from some pesky, itchy eyes at age 4 to asthma at age 16,” he said.

In fact, Falcetano said that clinicians should concentrate on ensuring that patients who have both allergic asthma and pet allergies get the best management possible, and the diagnostic tools to ensure this care are already available.

“They’re available in all the national laboratories, many regional laboratories and even local hospital-based laboratories,” he said. “Smaller laboratories are adding them on a regular basis.”

The precise diagnosis based on the components of these pet allergens sets the course for the interventions that follow, Falcetano said.

“You improve the diagnosis, you improve the management advice, you improve the treatment,” he said.