For thousands of years, we have been trying to craft our ideal canine companions. We have honed their abilities to perform an array of specific tasks, from fetching waterfowl to staring down wayward sheep. We have reshaped and refined their bodies, producing sausage-shaped dachshunds, polka-dotted Dalmatians, bushy-browed schnauzers and deeply wrinkled Shar-Peis.

And we have done it using nothing more sophisticated than good old-fashioned selective breeding. Now our canine engineering efforts are entering a new era. Earlier this month, Kindred Companion Sciences, a biotech start-up based in New York, revealed that it had used the technique known as CRISPR to create the first gene-edited, hypoallergenic dogs.

Thanks to a single genetic tweak, the dogs — two undeniably adorable beagles — appear unable to produce a protein that can leave some people red-eyed and wheezing. Still, it’s a long way from the lab to the laps of pet owners across America. (It’s been two and a half years since scientists announced a gene-edited, hypoallergenic cat, but such felines are not yet available to the public.) More time and data are needed to determine whether Kindred has truly delivered on its promise of hypoallergenic dogs, experts said. Can a single gene edit reliably stave off the sniffles in humans? An even more critical question: What does it mean for dogs? Will our efforts to create pets that are more convenient for us have unintended health consequences for them? History is not encouraging.

Since the Victorian era, when dog fanciers began to create and codify modern dog breeds, our quest for the perfect pooch has yielded dogs that are inbred, disease-prone and saddled with extreme physical traits — super flat faces and ultra long backs — that compromise their welfare."We’ve created an enormous amount of inherited diseases in dogs, often unintentionally, because of our pursuit of certain traits that appeal to us," said Rowena Packer, an expert on companion animal welfare at the Royal Veterinary College in London. "I just think we have a lot more responsibility to think more critically about the dogs that we create."Dog design For all the canine diversity we’ve managed to create through selective breeding, a truly hypoallergenic dog remains something of a holy grail. Breeders have created all manner of low-shedding dogs and purportedly hypoallergenic dogs (behold the labradoodle and all of its doodle-y descendants). But these dogs still produce proteins that, secreted through their skin, saliva and urine, can trigger human allergies.

Gene editing provides a “simple, elegant” way to solve the problem at the source, said Matt Walker, the co-founder and chief executive of Kindred, who has suffered from dog allergies his whole life. Kindred began with canine cells, using CRISPR to disable a gene known as Can f 1, which codes for one of the main canine allergens. Then, the scientists used a basic cloning technique to transfer the edited genomes from these cells into dog embryos.

They implanted the embryos in a surrogate beagle mother, who gave birth to two puppies: Alfie and Bailey, who are now almost 2 years old. The company has detected no trace of the allergen in either dog, and Dr. Walker, who adopted Bailey, has experienced no allergic reactions. (Alfie was adopted by one of Dr. Walker’s colleagues.) The dogs appear to be developing normally."No red flags, no yellow flags — so far, the animals seem completely healthy," Dr. Walker said. "That said," he added, "this is the starting point of our work."Indeed, for all its purported precision, gene editing can have unpredictable consequences. Medical issues might appear later in the dogs’ lives, or when the company starts producing enough dogs to spot rare side effects.

Or, of course, they could turn out to be perfectly healthy.