For years, Matt Walker, a lifelong dog lover, couldn't indulge his passion without suffering severe allergic reactions. Now, thanks to a groundbreaking gene-editing technique, he can enjoy the companionship of Bailey, a hypoallergenic beagle, free from sneezes and rashes.

Mr. Walker, a geneticist, can now feed Bailey peanut butter and play fetch with her, a stark contrast to his previous experiences. The key to this transformation lies in Bailey's saliva and hair, which no longer contain a crucial allergy-causing protein.

"The feeling right now is sort of a mix of relief and awe and gratitude that it worked," Mr. Walker stated, whose company, Kindred Companion Sciences, developed Bailey and her twin, Alfie, using the Nobel Prize-winning CRISPR technology.

While this breakthrough offers hope to millions of dog allergy sufferers, it will be years before such animals are widely available. Scientists must meticulously monitor the long-term health effects of the genetic modification and devise methods to commercialize the approach affordably. Furthermore, experts not involved in the research raise ethical concerns.

Arthur Caplan, a bioethicist with New York University's Grossman School of Medicine, cautioned, "It opens the door to a lot more people being able to own pets. On the negative side, it may discourage people from trying to use strays and unwanted animals that are not engineered to be allergy-free."

Previous attempts to create hypoallergenic pets, primarily through cloning, often resulted in less healthy animals due to excessive genetic similarity. Two years ago, researchers used CRISPR to reduce allergy-causing proteins in a cat named Alsik, but the safety of this technique for broader feline application remains unconfirmed.

It's also a common misconception that breeds like poodles are truly hypoallergenic; while they shed less, they still produce allergy-triggering proteins.

To create Alfie and Bailey, scientists began by editing the genetic code within dog skin cells, effectively deactivating the primary gene responsible for producing allergy-causing proteins. This modified genetic code was then transferred into eggs, which were implanted into a beagle surrogate.

The surrogate gave birth to two healthy female pups in September 2024. Subsequent tests of their saliva and fur confirmed the absence of the targeted allergy-causing protein.

Further validation came from an allergy test performed on Mr. Walker himself. His skin reacted to extracts from a poodle and a goldendoodle, but showed no reaction to samples from Alfie and Bailey's saliva and dander. This research, published in the CRISPR Journal, marks the first successful application of such an approach in dogs.

Mr. Walker noted that all dogs share the same allergy-causing gene that was edited in Alfie and Bailey. Kindred Companion Sciences aims to expand testing to other dog breeds and service animals, with the goal of developing allergy-free lines beyond beagles.

However, Dr. Jeff SoRelle, a pathologist at the University of Texas Southwestern Medical Center, who was not involved in the study, suggested that future research should test these gene-edited dogs on a wider range of people with pet allergies to confirm their efficacy across the human population.

He also pointed out that the switched-off gene is the main, but not the sole, allergy-causing culprit, meaning "we don't exactly know just how effective or broadly useful this could be for stopping dog allergy in humans."

Bailey currently resides with Mr. Walker in New York, while Alfie lives in Florida with another Kindred scientist. The genetic edit, though rare, occurs naturally in some dogs, leading Mr. Walker to believe it's unlikely to cause negative health effects. Nevertheless, routine veterinary monitoring will be crucial.

Mr. Walker has had Bailey for a little over a year, and she has become an integral part of his family. Despite his lifelong love for dogs, his allergies had always prevented him from having one, even with breeds like his family's goldendoodle causing him itchy eyes and painful rashes. Now, he and Bailey can enjoy simple pleasures like playing tug-of-war and her comforting presence when he's unwell.

"It feels just amazing to get to have a dog," Mr. Walker expressed.