Why Is Chocolate Bad for Dogs?

iStock / MirasWonderland
iStock / MirasWonderland

Chocolate is toxic to dogs and a number of other animals because it contains alkaloid chemicals called methylxanthines - namely, theobromine (3,7-dimethylxanthine) and caffeine (1,3,7-trimethylxanthine). Both of these stimulate the nervous and cardiovascular systems. It’s an effect that humans seek out, and we can get away with it because we metabolize the chemicals relatively quickly. Other animals process them more slowly, so the effects are more pronounced.

If a dog eats too much theobromine and caffeine, they’ll start to show a number of symptoms, including diarrhea, vomiting, muscle spasms, excessive panting, hyperactive behavior, seizures and dehydration. They may become hyperthermic, go into respiratory failure or experience cardiac arrhythmia, all of which can cause death.

So, how much chocolate is too much for a dog? Depends on the size of the dog, and the kind of chocolate. The amount of methylxanthines in chocolate varies among different chocolate products and brands. In general, though, dry cocoa powder has the most, with around 800 milligrams per ounce, according to the Merck Veterinary Manual. Unsweetened baker’s chocolate (~450 mg/oz), semisweet and sweet dark chocolate (~150-160 mg/oz) and milk chocolate (~64 mg/oz) follow.

Based on their experience and research, the ASPCA Animal Poison Control Center considers 100 to 200 milligrams of methylxanthines per kilogram of dog to be a lethal dose. Mild symptoms can happen with doses as small as 20 mg/kg and severe symptoms, including seizures, can happen at 40-60 mg/kg. Given those numbers, as little as four ounces of dark chocolate could cause problems for a average-sized, 60lb Labrador Retriever, America’s most popular breed. How much chocolate can your dog handle before trouble starts? National Geographic has a handy calculator to figure out the amount based on your dog’s weight and the type of chocolate.

If a dog does eat a toxic dose of chocolate, there’s not much that can be done for it outside of a vet’s office if the methylxanthines make it into the dog’s bloodstream and start circulating through the body. In her book, Help!: The Quick Guide to First Aid for Your Dog, veterinarian Michelle Bamberger recommends slowing or stopping this process by the body by trying to make the dog vomit. Don’t try sticking your fingers down its throat, though. Instead, feed it a small dose (a teaspoon) of hydrogen peroxide or table salt. Your vet can handle things from there, and treatment usually involves giving the dog activated charcoal to bind to the toxins and using intravenous fluid therapy to flush them out.

Methylxanthines in chocolate are toxic for other animals, too. Cats are especially susceptible because of their small size. Luckily for them, cats lack the taste receptors that pick up “sweet” tastes, and rarely have much motivation for eating more than a nibble or two of chocolate. Both horses and humans are less susceptible to chocolate toxicity thanks to their size and faster metabolization of the chemicals. Methylxanthine poisoning can still happen to people who consume large amounts of chocolate or coffee in a small timeframe, though, and the amount of caffeine in a strong cup of coffee is enough to cause symptoms in a small child.

Why Are Barns Often Painted Red?

iStock/Ron and Patty Thomas
iStock/Ron and Patty Thomas

Beginning with the earliest American settlements and continuing into the 18th century, most barns weren't painted at all. Early American barn builders took sun exposure, temperature, moisture, wind, and water drainage patterns into account when placing and building barns, and they seasoned the wood (that is, they reduced the moisture content) accordingly. The right type of wood in the right environment held up fine without any paint.

Toward the end of the 1700s, these old-school methods of barn planning and building fell by the wayside. People sought a quicker, easier fix for preserving their barns—a way to coat and seal the wood to protect it from sunlight and moisture damage. Farmers began making their own coating from a mix of linseed oil (a tawny oil derived from the flax seeds), milk, and lime. It dried quickly and lasted a long time, but it didn't really protect the wood from mold and wasn't quite like the "barn red"we know today—it was more of a burnt orange, really.

Turning Red

The problem with mold is that it decays wood and, in large quantities, can pose health risks to people and animals. Rust, it turns out, kills mold and other types of fungi, so farmers began adding ferrous oxide (rusted iron) to the linseed oil mix. A little bit of rust went a long way in protecting the wood, and it gave the barn a nice red hue.

By the late 19th century, mass-produced paints made with chemical pigments became available to most people. Red was the least expensive color, so it remained the most popular for use on barns, except for a brief period when whitewash became cheaper and white barns started popping up. (White barns were also common on dairy farms in some parts of Pennsylvania, central Maryland, and the Shenandoah Valley, possibly because of the color's association with cleanliness and purity.)

Throughout Appalachia (a historically poorer region), many barns went unpainted for lack of money. In the tobacco regions of Kentucky and North Carolina, black and brown barns were the norm, since the dark colors helped heat the barn and cure tobacco.

Today, many barns are still painted the color traditionally used in a given region, with red still dominating the Northeast and Midwest.

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This story was updated in 2019.

Is There An International Standard Governing Scientific Naming Conventions?


Jelle Zijlstra:

There are lots of different systems of scientific names with different conventions or rules governing them: chemicals, genes, stars, archeological cultures, and so on. But the one I'm familiar with is the naming system for animals.

The modern naming system for animals derives from the works of the 18th-century Swedish naturalist Carl von Linné (Latinized to Carolus Linnaeus). Linnaeus introduced the system of binominal nomenclature, where animals have names composed of two parts, like Homo sapiens. Linnaeus wrote in Latin and most his names were of Latin origin, although a few were derived from Greek, like Rhinoceros for rhinos, or from other languages, like Sus babyrussa for the babirusa (from Malay).

Other people also started using Linnaeus's system, and a system of rules was developed and eventually codified into what is now called the International Code of Zoological Nomenclature (ICZN). In this case, therefore, there is indeed an international standard governing naming conventions. However, it does not put very strict requirements on the derivation of names: they are merely required to be in the Latin alphabet.

In practice a lot of well-known scientific names are derived from Greek. This is especially true for genus names: Tyrannosaurus, Macropus (kangaroos), Drosophila (fruit flies), Caenorhabditis (nematode worms), Peromyscus (deermice), and so on. Species names are more likely to be derived from Latin (e.g., T. rex, C. elegans, P. maniculatus, but Drosophila melanogaster is Greek again).

One interesting pattern I've noticed in mammals is that even when Linnaeus named the first genus in a group by a Latin name, usually most later names for related genera use Greek roots instead. For example, Linnaeus gave the name Mus to mice, and that is still the genus name for the house mouse, but most related genera use compounds of the Greek-derived root -mys (from μῦς), which also means "mouse." Similarly, bats for Linnaeus were Vespertilio, but there are many more compounds of the Greek root -nycteris (νυκτερίς); pigs are Sus, but compounds usually use Greek -choerus (χοῖρος) or -hys/-hyus (ὗς); weasels are Mustela but compounds usually use -gale or -galea (γαλέη); horses are Equus but compounds use -hippus (ἵππος).

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