Science Q & A

Poison for pets but not for me?

New York TimesNovember 10, 2013 

Q. I know chocolate is harmful to dogs. What else hurts pets but not people?

A. Dogs and cats are commonly poisoned by drugs intended for humans, and several foods are uniquely toxic to dogs, said Dr. Karyn Bischoff, a veterinarian and toxicologist with the New York State Animal Health Diagnostic Center at Cornell University.

Bischoff listed canine food risks including the artificial sweetener xylitol, macadamia nuts, onions, garlic, leeks and chives. Grapes and raisins sometimes pose a threat; since the consequence could be life-threatening kidney failure, she said, “Why would you take the risk?”

As for chocolate, humans seem to be a little more resistant than dogs and cats to stimulants in it that are similar to caffeine, but even humans can get sick after consuming too much, Bischoff said. Baking chocolate, cocoa and dark or semisweet chocolates are the most dangerous.

Part of the problem with drugs is that cats and most dogs are relatively small, so a human dose is far too much. But Bischoff noted that some drugs, including acetaminophen in cats and ibuprofen in dogs, are toxic to pets because of their unique metabolism.

Dogs are often poisoned when they consume spilled medications, she said. Cats do so less frequently, but seem to be attracted to the antidepressant venlafaxine (Effexor), and Adderall, used to treat attention deficit hyperactivity disorder.

A more complete list of pet poisons of all kinds can be found on the ASPCA website: http://bit.ly/12J9KRM.

Your boiling joints

Q. Why do necks “crack”?

A. “Because the joints boil when they are stretched,” said Dr. Christopher Visco, director of sports medicine at NewYork-Presbyterian/Columbia University. The mechanism, involving the release of gas bubbles, “works for any joint in the body surrounded by a capsule, such as knuckles.”

The neck has a series of paired joints, called facet joints, that run up and down each side. Each is filled with a bit of fluid and is surrounded by a capsule.

“When someone bends his or her neck, the capsule surrounding each joint is stretched out,” Visco said. “This decreases the pressure on the fluid in the joint.”

The lower the pressure on a fluid, the closer it gets to changing from liquid to gas.

“This is called boiling. Another term is cavitation,” Visco said. “If someone decreases the pressure on any fluid enough, eventually that fluid will release its gas. And in the case of the neck pop, you hear a crack as the gas pops out of the fluid.”

Generally, joint cracking is not harmful, Visco said, but when extreme stretching becomes a habit (to relieve tension, for instance), it can cause irritation of soft tissue or cartilage. And because important nerves and blood vessels run through the neck, amateur neck-cracking is ill-advised. A gentle stretching routine is preferable.

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