Common allergy medication can be deadly to pets

Tiffany Day, a travel nurse, and her beloved Labrador retriever mix, Luna, had just arrived in New Mexico after a long drive from Illinois. Exhausted from the journey, Day realized she needed a few items from the store and left Luna in their home, along with an open travel bag. This decision would soon lead to a distressing ordeal involving a call to the Pet Poison Helpline.

"It was a horrible day," Day said. "Luna and I had just returned from an assignment in Illinois, and I was exhausted. I thought, 'She's tired; she won't get into anything,' so I ran out for a quick trip to the store. When I got home, I found a chewed-open bottle of allergy pills on the floor, and it was clear Luna had ingested some of the medication. I'd never heard there was a problem with giving pets allergy pills like Benadryl, so I wasn't too worried at first. But as the night went on, she began barking at nothing, swaying and walking into walls. That's when I knew she needed a veterinarian."

Day quickly took Luna to the Roadrunner Veterinary Emergency & Specialty Hospital in Algodones, a village in Sandoval County. Upon arrival, the hospital team immediately contacted the toxicology experts at Pet Poison Helpline to develop a treatment plan tailored to Luna's situation.

"Many people give their pets human allergy medications that contain diphenhydramine," said Dr. Renee Schmid, a senior veterinary toxicologist and director of veterinary services at Pet Poison Helpline. "In most cases, a small dose is safe for pets. However, if the dose is too high, it can result in dangerous reactions, including agitation, lethargy, abnormal heart rate, vomiting, diarrhea and even seizures or respiratory depression. In severe cases, like Luna's, the ingestion could be fatal."

The medical team treated Luna with medical-grade activated charcoal, but it had been too long since the exposure to fully prevent signs of toxicity. Luna was given an antiemetic to prevent vomiting, placed on intravenous fluids and sedated to manage her agitation. The team closely monitored Luna overnight to ensure she did not develop more severe symptoms.

Despite the scare, Luna was able to go home the following day. However, soon after her recovery, Luna developed a condition called immune-mediated thrombocytopenia (IMTP), a likely unrelated disorder that ultimately led to her passing.

"IMTP is a condition where the pet's immune system attacks its own platelets, leading to their premature destruction," Schmid said. "It is the most common hemostatic disorder in dogs and can be either primary and idiopathic or secondary to an infectious, parasitic or immune-mediated disease. In Luna's case, the medical team could not determine the cause."

Common signs for IMPT include weakness, lethargy and bleeding for unknown causes.

Pet Poison Helpline created “Toxin Tails" to educate the veterinary community and pet lovers on the many types of poisoning dangers facing pets, both in and out of the home. All the pets highlighted in “Toxin Tails” have been successfully treated for the poisoning and fully recovered.

While Luna's story ended tragically, Day hopes that sharing her experience will raise awareness about the dangers of human medications for pets.

"Even though Luna later passed from a different condition, I wanted to share her allergy medication story," Day said. "If telling her story can help even one other pet, it will be worth it. You have to be on your game at all times. Keep all medications, even those you think are safe for your pets, out of reach. You don't think they'll get into it, but they will."