Dogs and cats often have a penchant for eating strange things. Whether by instinct or hunger, or simply the mysterious behavior that pets are known to have; cats will often gravitate toward plastic or wool, and many a dog will chew on whatever it can get its chops around. Unfortunately, the results can be less than positive. A chewed shoe is one thing, but a chewed prescription medication bottle and its contents are another.

Every year the ASPCA compiles a list of the top substances toxic to pets based on calls from the previous year. In 2010, the ASPCA Animal Poison Control Center (APCC) in Urbana, IL, fielded more than 167,000 phone calls about pets exposed to poisonous substances. Here is the list of top toxins:

1. Human Medications Human medications topped the list of pet toxins for 2010. A quarter of the center’s calls were about medications ingested by pets. The most common ones were over-the-counter medications such as ibuprofen and acetaminophen, as well as antidepressants and ADHD medications.

If you have unused medication, though, do not flush it down the toilet! much of our water supply is tainted with pollution from medication. Instead, find out how to properly dispose of medicine in a way safe to pets, wildlife, and the environment.

See How to Dispose of Prescription Drugs.

2. Insecticides Around 20 percent of the calls to the APCC were for concerns about insecticides; including those used for fleas and ticks as well as those used around the house. Believe it or not, the most serious poisonings occur when products not labeled for use on cats are used on them.

For more, see Safe Flea Repellents for Cats.

3. Rodenticides if you use them, be sure to use rat or mice poison only in a place where your pets can not access them. these baits are generally grain based and created to be attractive vermin, but cats and dogs like them too. some rodenticides can cause seizures, internal bleeding or kidney failure.

Best bet? Use a humane mousetrap.

4. Human Food who hasn’t shared some nibbles with their pet? While some snacks may be okay, others are clearly off-limits. Xylitol, grapes, raisins, onions and garlic are commonly eaten by pets–not good. Grapes and raisins can cause kidney failure in dogs, while onions and garlic can cause anemia if enough is ingested. Xylitol, a sugar alcohol used to sweeten sugar free gums and mints, can cause low blood sugar and liver failure in dogs.

See the surprising list: Top 10 Foods Poisonous to Pets.

5. Veterinary Medications Like children’s medications, many medications made for our pets are flavored for ease of giving. Unfortunately, that means that animals may ingest the entire bottle of medication if they find it tasty. Common chewable medications include arthritis and incontinence medications. Contact your veterinarian if your pet ingests more than his proper dose of medication.

For more, see Care for Your Pet the Green Way.

6. Chocolate Chocolate can be very toxic to dogs. Unsweetened baking chocolate is the most dangerous of all chocolates, since it contains almost 10 times the amount of theobromine and caffeine as milk chocolate. Just one ounce (1 square) of unsweetened baking chocolate can kill a 10-pound dog (figure about 1/4 ounce for every 2.2 pounds as a fatal dose). Baker’s chocolate contains 390 milligrams of theobromine per ounce. Semisweet chocolate is the next most serious threat, containing 150 milligrams of theobromine per ounce. One ounce of this type of chocolate can kill a 3-pound dog. Milk chocolate contains 44 milligrams of theobromine per ounce.

Read more all about symptoms and other tips having to do with chocolate in Dog Chocolate Danger.

7. Household Toxins Harsh cleaning supplies like bleach, acids, alkalis and other detergents, can cause corrosive injury to the mouth and stomach, as can other items such as batteries and air fresheners.

To get toxic cleaning products out of your house and away from your pets, learn about these Five Basics for Nontoxic Cleaning.

8. Plants For decades, poinsettias have been thought to be poisonous to pets, while in truth, they’re not. however, there are a number of surprising plants, both indoor and outdoor varieties, that can be quite toxic if ingested by our pets. Lilies can cause life-threatening kidney failure in cats, while sago palms can cause liver failure in dogs and cats.

Keep indoor plants and flower arrangements out of reach to pets. Outside plants are harder. you can add bran flakes to your dog’s food to boost fiber which should quell cravings for vegetation.

For a list of top plants to avoid, see 24 Common Plants Poisonous to Pets.

9. Herbicides Lawn and garden chemicals include some of the most hazardous products in the home. Products that you use to kill insects, weeds, and fungal diseases may also be toxic to children, pets, birds, fish, and beneficial insects such as bees and ladybugs. Many herbicides have a salty taste that pets take a liking to. always follow label directions and keep pets off treated areas until they are dry.

Better yet, try some nontoxic alternatives that are surprisingly effective: 11 Ways to Control Weeds Without Chemicals

10. Outdoor Toxins Antifreeze, fertilizers and ice melts are all substances that animals can find outdoors. Antifreeze (ethylene glycol) has a sweet taste that attracts pets. even in small amounts, antifreeze is lethal to all animals, but dog are probably most susceptible because of their tendency to taste everything. even a tablespoon of the liquid can be toxic or fatal to a small dog, depending of the size of the animal and the concentration of the product.

Cats are less likely to lap up unknown liquids, but they can walk through puddles of antifreeze on the floor, and then lick the chemical off the fur or feet. even a teaspoon can be fatal to a cat. keep these items in securely locked sheds or on high shelves where pets cannot get to them!

For symptoms and advice on antifreeze poisoning, see Pets and the Dangers of Antifreeze.

If you have any reason to suspect your pet has ingested something toxic, contact your veterinarian or the Animal Poison Control Center’s 24-hour hotline at (888) 426-4435.

Related:

• Poison Safety Kit for Pets
• First Aid for Pets Burns and Scalds
• Does Your Cat Eat Strange Things