Hold the turkey skin and fatty gravy—your pet will thank you later.

If you have a sumptuous feast to look forward to on Thanksgiving Day, it might be tempting to share the bounty with your pet. But it’s a bad idea. A lot of ingredients that might show up in your holiday spread (or unguarded trashcan) are harmful to pets. Dogs, being more inclined than cats to scarf down human food, are especially vulnerable.

When holiday foods don’t agree with a pet, they often cause vomiting and diarrhea, as well as more debilitating symptoms. So keep a close eye on your pets, and make sure to keep them away from these items in particular.

Grapes

Grapes and raisins are poisonous to dogs (cats rarely eat them.) They can cause vomiting and diarrhea before shutting down the kidneys.

Vets aren’t sure why this happens, or why some dogs seem to be more likely to get sick. “We would recommend treatment even if they only got into a few grapes and raisins,” says Erica Reineke, a professor of emergency and critical care medicine at the University of Pennsylvania’s School of Veterinary Medicine.

Treatment can include making the dog throw up and giving him activated charcoal to prevent more poison from being absorbed. “If they come in immediately and we’re able to induce vomiting and decontaminate them and support them with some IV fluids, it’s pretty uncommon that we end up seeing kidney failure,” Reineke says.

Onions

Garlic, onions, chives, or leeks may spice up stuffing and other side dishes, but they are dangerous for both dogs and cats. These foods damage the membranes of red blood cells, leading to anemia. “The red blood cells basically pop,” says Reineke.

After eating onions, pets might experience vomiting, diarrhea, weakness, pale gums, or a high heart rate. It can take awhile for symptoms to show up. “They may eat a bunch of onions and you think everything’s okay, and then two days later the dog or cat starts acting lethargic,” Reineke says.

Poisoning from onions happens less often than with other holiday foods. “We see it, but it’s certainly less common than chocolate, grapes, and raisins,” Reineke says.

Bones and fats

If your dog manages to swallow a bone, there’s a chance it will lodge in the intestines and need to be surgically removed.

Poultry bones can also splinter and irritate the esophagus or gastric lining. “If they’re just in the stomach and they stay there, they’ll eventually dissolve most of the time,” Reineke says.

Turkey skin is another font of gastrointestinal distress, as are gravy and fatty foods (like butter-drenched mashed potatoes or stuffing). “Worst case scenario, that can cause inflammation of the pancreas,” Reineke says. This condition, called pancreatitis, can be life-threatening.

Sweets

Cats show little interest in desserts, but several treats can endanger dogs. Chocolate is the usual suspect, particularly dark or baker’s chocolate. One 2017 study found that pups are most likely to get chocolate poisoning on Christmas—but that study was done in the U.K, and it's reasonable to imagine that in the U.S., Thanksgiving doesn't lag too far behind. Any occasion when numerous desserts sit out amidst general household chaos is potentially dangerous.

How much damage chocolate does depends on a dog’s weight and how much they've eaten. “If they eat one Hershey’s kiss that’s probably not an issue,” Reineke says. You should check how much they've consumed and call a vet for advice, or use an online dose calculator to make sure they're not in peril.

Chocolate contains theobromine, a substance similar to caffeine, which, at higher doses, can cause vomiting, diarrhea, an elevated heart rate or blood pressure, and even, rarely, seizures and coma. “They might be anxious, they might be running around more than they normally would, ” Reineke says.

Another troublemaker is xylitol, an artificial sweetener that sometimes appears in baked goods. It can cause a dangerous drop in blood sugar or, in some dogs, liver failure.

Alcohol

Booze and rum-soaked cakes are not a good way to share your festive spirit with your pet. Like people, animals can suffer from alcohol poisoning, and may experience vomiting, falling blood pressure and body temperatures, loss of coordination, or coma.

Another, less obvious source of alcohol: yeast dough. If your dog gobbles up uncooked bread dough, it can continue to rise in the stomach, fermenting and releasing alcohol. This can also lead to bloating or even a twisted stomach.

Are any Thanksgiving foods safe?

If you are worried about something your pet might have eaten, you can contact a veterinarian or call the Pet Poison Hotline or ASPCA Animal Poison Control Center.

Even if a dish isn’t toxic, it’s still probably not ideal for your furry friends. “We would discourage pet owners from giving table food at any time because it can cause GI upset if it has a lot of fat in it and they’re not used to eating it,” Reineke says.

Still, there is one Turkey Day staple that might actually do your pet some good: pumpkin is full of fiber, so it’s sometimes used as a remedy for constipated dogs. But if you're not trying to make Fido and Fluffy poop, it's best to give them treats of their own.

Written by Kate Baggaley for Popular Science and legally licensed through the Matcha publisher network. Please direct all licensing questions to legal@getmatcha.com.