Anthony Shadid (Steven Senne/AP)

The passing of legendary New York Times foreign correspondent Anthony Shadid is shocking on many levels. Two of them:

One, that a 43-year-old with seemingly decades of work ahead of him on a region that’s so pivotal to the world would be lost to the profession. Two, that a veteran of the world’s diciest war zone would be felled by an asthma attack.

According to the New York Times, Shadid's allergies were twice set off when he approached horses as he trudged in and out of Syria on assignment for the paper. With him was Times photographer Tyler Hicks:

It was on that first night, Mr. Hicks said, that Mr. Shadid suffered an initial bout of asthma, apparently set off by an allergy to the horses, but he recovered after resting.

On the way out a week later, however, Mr. Shadid suffered a more severe attack — again apparently set off by proximity to the horses of the guides, Mr. Hicks said, as they were walking toward the border. Short of breath, Mr. Shadid leaned against a rock with both hands.

At that point, Shadid collapsed and died.

James Sublett, M.D. and a fellow at the American College of Allergy, Asthma and Immunology (ACAAI), termed Shadid's death “tragic.” Sublett is based in the horse country of Louisville, Ky., and he sees at lot of patients who suffer from reactions to horses. “We routinely test for horse allergies,” says Sublett. “Riders, trainers and jockeys and people who work on the horse farms” are among the victims, says Sublett, noting that the affected are also “people who live near these places and get allergens in the air.”

Though horse allergies are common, Sublett says that much less is known about horse allergens than those of dogs and cats. Researchers, he says, have carefully identified the allergens in dogs and cats that cause pet lovers so much grief. According to ACAAI, approximately 10 percent of the U.S. population “may be allergic to animals.”

An Italian study found that 5 percent of a test population showed sensitivity to horse allergens. Whatever the numbers, furry animals like cats, dogs and horses are expert carriers of asthma-inducing material: The allergens, says Sublett, are “found throughout the animal — not only in the pelt, but in the glandular secretions, urine, and saliva.” And those allergens can “cross-react,” meaning that animals can sort of pollinate one another into galloping asthma bombs.

The science, in other words, signals that what befell Shadid is altogether too plausible. “If a person has a lifetime history of asthma, they should make sure they are evaluated and find out what kind of risk they may have,” Sublett says. But he notes: “He may have had the most expert care and still run into this.”