My very good friend Buster, who never misses an opportunity to watch me in the kitchen, was observing me make breakfast this morning. He showed special interest in the raisins that I put on my cereal.

Raisins and grapes are believed to be toxic to dogs. I use the word believed because it has not been proven conclusively that grapes and raisins themselves are toxic. Some scholars suspect mold or fungus present on the fruits is what causes kidney damage in some dogs that eat them.

Regardless of the toxin’s identity, you should not let your pet eat grapes or raisins.

What truly strikes me is not that grapes and raisins are toxic to dogs. Plenty of human foods should not be eaten by pets (chocolate is another example). The interesting thing, to me, is that nobody thought that grapes or raisins were dangerous before 1999. Before that, many vets recommended grapes as a healthy, tasty dog treat.

Our understanding of the world and its systems is continually evolving. Accepted truths are upended regularly. The body is very complex. There will be more surprises in the future.