Nothing to Sneeze At: New Strategies for Controlling Cat Allergy

in Asthma, Indoor Allergies, News, Pets
Published: October 13, 2020
New Strategies for Controlling Cat Allergy. Cat getting it's face rubbed.
Photo: Getty

When it comes to cat allergy, there’s only one sure way to avoid symptoms – stay away from cats. But many cat lovers with allergies would rather live with the sniffling, sneezing and wheezing than live without their beloved pet. 

“As I tell people with cat allergies, the treatment of choice is removal of the cat,” says Dr. Michael Blaiss, executive medical director of the American College of Allergy, Asthma and Immunology (ACAAI). “Most people don’t want to give up the cat. Usually, they will remove me as the doctor before they remove the cat.”

Cat allergy is the most common animal allergy, affecting about one in five adults worldwide. Symptoms range from stuffy nose and itchy eyes, to hives, wheezing and asthma attacks.

Immunotherapy, often called allergy shots, can be effective in taming reactions in many people. But immunotherapy requires several years of injections, which many people don’t want to do.

The good news is that researchers are on the hunt for new treatments – and developing some promising new options. This article explores the novel therapies under study, including lab-created antibodies that help to halt allergic reactions in their tracks, and even a vaccine for kitty, designed to trim the amount of allergens that cats shed.  

And some relief may be as near as your local pet store. In 2020, Nestlé Purina began selling cat food that neutralizes allergens in the cat’s saliva, a source of the protein that causes so much itchy, watery, wheezy misery.

Cat Allergen: It’s Everywhere

The major culprit in cat allergies is “Fel d1,” a protein excreted in the cat’s skin, saliva, and urine. When cats lick themselves, they deposit Fel d1 on their fur. When the cat sheds, the allergens on the hair and dander (dried skin particles) spread.

And do they ever spread. Fel d1 proteins are small, so they remain suspended in the air. Fel d1 is also sticky, and takes a long time to decompose, Blaiss explains. The proteins cling to surfaces like draperies, carpets, furniture, bedding, clothing, even walls and ceilings.

Because of this, cat allergens are notoriously difficult to remove from a home, even with cleaning and vacuuming. Research has shown that there are cat proteins in almost all U.S. homes, even in homes where there are no cats. In school classrooms, kids can bring in enough Fel d1 on their clothes and backpacks to trigger asthma symptoms in their allergic classmates.

Bathing cats can cut down on Fel d1 in the fur, but only for a day or so. Studies have found female cats produce a lower level of allergens than males, while neutered males produce lower levels than unneutered males – but they all produce plenty.

Current Cat Allergy Treatments 

If avoiding cats isn’t possible, or you just really, really want a cat despite an allergy, Blaiss recommends at a minimum to never allow the cat inside your bedroom, where you spend about eight hours a day.

Products such as antihistamines, nasal steroids and asthma medications can provide some relief. But medications treat symptoms, not the cat allergy itself. To do that, you need immunotherapy, which is given as shots in an allergist’s office.

Immunotherapy retrains the immune system to tolerate more cat protein without reacting. Typically, patients go to an allergist’s office for weekly injections with small amounts of cat protein during a buildup phase that lasts for several months. That’s followed by monthly “maintenance” injections for three to five years.

Research shows that cat immunotherapy can reduce symptoms in many people, and that the results last. But some people react to the injections, while others quit because of the inconvenience of as many as 80 injections in all.

“A lot of people quit before three years. There really is a need to get the duration of it down,” says Dr. Harold Nelson, an allergist at National Jewish Health in Denver.

Some allergists offer sublingual immunotherapy (SLIT), which uses liquid drops of cat extract placed under the tongue. But this treatment is not approved by the U.S. FDA, so allergists offering it are doing so “off-label.” Nelson says that without clinical trials to confirm dosage and efficacy, there is no way for patients to know if the formulation has the right amount of cat protein to develop tolerance.

Speeding Up Immunotherapy

Given how many people have cat allergies, there is huge interest in finding treatments that are both quick and lasting.

A few years ago, the allergy field was excited about cat immunotherapy designed to desensitize patients in a mere four allergy shots. Called Cat-SPIRE, this vaccine involved breaking down Fel d1 protein into a few of its minuscule and basic parts, called peptides. The peptide shots worked great in studies in an environmental exposure chamber (a room constructed to expose people under controlled conditions to a particular allergen). However, the results didn’t pan out in a Phase 3 trial of 1,500 patients, says Nelson, the trial’s principal investigator. Researchers were never sure exactly why.

However, the possibility of speeding up immunotherapy remains tantalizing. Researchers with the Immune Tolerance Network have recently completed a clinical trial, called CATNIP, looking at whether cat immunotherapy shots combined with a biologic drug can cut down the time it takes to desensitize patients to Fel d1 to one year.

The drug, tezepelumab, is a monoclonal antibody (an antibody produced in a lab) designed to block allergic reactions. It does this by targeting thymic stromal lymphopoietin or TSLP, a key chemical messenger that kick-starts and drives the allergic inflammatory response. Tezepelumab has shown good results in clinical trials for severe asthma.

The CATNIP study enrolled 120 cat-allergic participants in a blinded, controlled study, in which patients didn’t know whether they were getting a monthly dose of tezepelumab plus weekly cat immunotherapy – or just getting one or the other of those treatments alongside a placebo. A final group got placebo of both the drug and allergy shots.

All patients were treated for about a year, with two rounds of testing for allergy symptoms and blood markers in the year after therapy.

“The goal is to see if the addition of tezepelumab might augment the effects of immunotherapy, and work in a synergistic way,” explains Dr. Jonathan Corren, principal investigator and a clinical faculty member at University of California, Los Angeles. Investigators will soon submit the results of the proof-of-concept study for publication.

Antibody-Blocking Approach

Another approach that involves lab-created antibodies to blunt cat reactions is being studied by Regeneron Pharmaceuticals, the maker of the asthma and eczema drug Dupixent (dupilumab).

A key step in allergic reactions occurs when IgE antibodies circulating in the bloodstream bind with the allergen, in this case, Fel d1. In a study published in the journal Nature, researchers created two versions of a protective type of antibody, IgG, that blocks IgE from binding to the cat protein.

About 70 participants were either given a single shot of the IgG antibodies, or a placebo. The study found the IgG antibodies reduced allergic symptoms in 60 percent of participants. As well, the effect persisted at a one-month follow-up, Jamie Orengo, PhD, Regeneron’s executive director immunology and inflammation research, told Allergic Living.

Research is ongoing, and Regeneron is planning a larger clinical trial to determine how often injections would be needed, and how long effects last. 

But Nelson throws some cold water on the approach. Medications containing monoclonal antibodies are very expensive, and if multiple doses are needed, he says the approach may not prove practical.

Vaccinating Kitty

New Strategies for Controlling Cat Allergy. Little girl playing with cat in a table.
Photo: Getty

Here’s another option: Why not have the cat get the shots? Researchers in Switzerland are investigating whether a vaccine, called HypoCat, can be administered to felines to reduce their allergen load.

This vaccine uses a virus-like particle to provoke the cat’s immune system to immunize it against its own allergenic protein. The vaccine prompts the cat to develop antibodies that bind with and neutralize Fel d1. The idea is that this will reduce allergy symptoms in human pet owners.

Over 50 cats were treated with the vaccine, which was administered three times over the course of six weeks. Researchers found the vaccinated cats made antibodies to Fel d1, and had a reduction of Fel d1 in their tears. The study was published in the Journal of Allergy and Clinical Immunology in July 2019. A small study published in March 2020 also found that seven out of nine cat owners whose pets were vaccinated reported fewer allergy symptoms, and they could interact with their cats longer.

Commercial availability of the vaccine is at least a few years away, since more clinical trials are required. The ACAAI’s Blaiss finds the approach promising. However, until there is a controlled study, he says the question remains as to whether symptom relief “is truly lasting or not.”  

Allergen-Reducing Cat Food  

As you await therapy developments, you may want to pick up a bag of Pro Plan LiveClear, sold by Nestlé Purina PetCare. According to the company, the new cat food is produced using eggs that contain an anti-Fel d1 antibody. When cats nibble on the kibble, the egg powder binds to Fel d1 in the cat’s saliva, neutralizing it.

During grooming, the cat transfers less allergen onto its skin and fur, without altering the levels of Fel d1 the cat produces. (It’s thought that Fel d1 may be important to the cat’s health).

A study published in 2019 found that after 105 cats ate the allergen-reducing food for three weeks, they had 47 percent fewer allergens in their fur. Pro Plan LiveClear hit the shelves of pet retailers and some veterinary clinics this spring.

Blaiss says if you’re allergic to your cat, the cat food is probably worth a try. “My concern is that it doesn’t block Fel d1 100 percent. But is it enough to make a difference? That may depend on the person, how much the cat is producing and how sensitive you are.”   

And while Fel d1 is the main driver of cat allergies, it isn’t the only one. Cats excrete several other proteins that allergic individuals may become sensitized to, so the cat food – and any treatments targeting Fel d1 – may not get rid of allergy symptoms completely.

With people increasingly working remotely and relying on their pets as a balm for loneliness, Nelson observes that the need to find better cat allergy treatments is more urgent than ever. “With everyone home, people are being exposed to even more cat allergen than ever,” he says.  

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Why “Pet-Free” College Housing Isn’t What It Seems