Your medicine cabinet may be hazardous to your pet’s health. This is where most people store various over-the-counter medications, painkillers, antihistamines, and vitamins.

“Dogs and cats are not small people. What is safe for people may not be safe for pets,” says Dr. Valentina Merola, a veterinarian at the University of Illinois College of Veterinary Medicine in Urbana. “Most human medication has the potential to cause severe problems.”

Acetaminophen, ibuprofen, naproxen, and aspirin are common anti-inflammatory drugs that can cause disease in dogs and cats even in small doses. Cats are especially sensitive to these medications. Their physiology is unique, and it is hard for them to clear certain drugs from their system. These pain medications can cause stomach ulcers and kidney damage in dogs and cats, and acetaminophen can also harm the liver.

Antihistamines and decongestants may contain pseudoephedrine, a drug that is poorly tolerated by dogs and cats. Even one pill can be a toxic dose. “It is extremely important to consult with a veterinarian before administering any drugs to pets. Similar appearing medications may actually contain different active ingredients. Some antihistamines are routinely prescribed by veterinarians to treat allergies, but other antihistamines, even those with very similar names, can contain pseudoephedrine or other dangerous ingredients,” explains Dr. Merola.

Dogs are notorious for chewing open bottles of medications and popping pills. If your pet ingests any human medication, call your veterinarian immediately. Your dog or cat may appear normal, but many of the toxic effects cannot be seen externally. Exposures at high enough doses can cause internal bleeding, stomach ulceration, and liver or kidney injury. Signs you will be able to recognize—such as vomiting and behavior changes—may not appear until hours after the exposure, when some damage may already be done.

“It’s critical to get these animals to the veterinarian for treatment in order to prevent damage. Drug therapy, fluids, activated charcoal, and gastrointestinal protectants may be needed. Supportive care and monitoring are very important,” says Dr. Merola.

Before calling your veterinarian, quickly gather the relevant facts, such as the exact name of the product your dog or cat ate and the active ingredients it contains. “How much was ingested is the magic question. Try to estimate this number by thinking how full the bottle was, how many pills it contained when full, and how many are missing. We need to deal with the worst-case scenario to provide proper care,” says Dr. Merola.

Your veterinarian will start by calculating the dose (measured by milligrams of drug per kilogram of body weight) your pet received. In addition the veterinarian will consider your pet’s health status and how long the drug has been in the animal’s system. These are all factors influencing the course of treatment.

To avoid an emergency situation, make sure all over-the-counter drugs are kept out of reach. Cats are able to climb high shelves and dogs may run into them during play, knocking bottles to the floor. Never leave medication on countertops! Dogs and cats will also raid purses and get into medication mischief.

Consult with your veterinarian before administering any medications. If you are concerned your pet has ingested any human medications, call your veterinarian or the ASPCA Animal Poison Control Center at 1-888-4ANI-HELP immediately.