Garlic & Onion: Though treated as a health food and often taken in supplement form by humans, garlic (along with its alliaceae cousins onions and leeks) is toxic-sometimes deadly-for pets, with reactions ranging from stomach damage to acute dermatitis to asthmatic attacks. Pets By Nature reports the story of a Pennsylvania woman who lost her Newfoundland to garlic poisoning: “Within two weeks of feeding a popular garlic supplement available at most pet stores and over the Internet, her Newfoundland developed a bleeding ulcer and perforated intestine.” The dog did not survive.

Grapes & Raisins: While not as toxic as members of the onion family, consumption of grapes and raisins can cause vomiting, dehydration and, in large quantities, kidney failure. The exact toxin present in grapes is not known, but scientists have established that both commercially and privately cultivated grapes, as well as raisins, present a risk.

Avocado: According to the American Society for the Prevention of Cruelty to Animals (ASPCA), avocado leaves, fruit, seeds and bark contain a toxic substance called Persin, which can cause vomiting, diarrhea and other gastrointestinal unpleasantness in dogs. While a medium-sized dog would have to consume a substantial quantity of avocado (picture a big bowl of guacamole) to become seriously ill, even a little bit is enough to cause an upset tummy.

Macadamia Nuts: Not widely consumed outside of Hawaii, macadamia nuts pose a stealth risk to canine health. The nuts can cause macadamia nut toxicosis, resulting in soreness, stiffness, and listlessness, according to Working Dog Magazine. The condition usually passes in 48 hours, but can lead to shock in severe cases.

Nutmeg: This popular spice, commonly used to season cakes, vegetables and even lasagna, should never be found on your dog’s dinner plate. Nutmeg, which has mild hallucinogenic properties, can cause seizures, tremors, central nervous system problems in dogs. In severe cases, shock and death have been reported.