Dog ate antihistamine Antihistamines are common medicines used to treat allergy symptoms such as runny nose, sneezing and itchy eyes. There are two main classes of antihistamines, the first generation antihistamines (also known as sedating antihistamines) and the second generation antihistamines. Following an overdose, the second generation antihistamines are more likely to cause significant poisoning as they are able to readily cross the blood brain barrier and enter the central nervous system.

Companion animals that ingest too much of an antihistamine can become sedated, disorientated and unsteady on their feet. More significant doses can result in dilated pupils, hyperactivity, agitation, tremors, an increase in the heart rate and potentially seizures. Some sedating antihistamines are also co-formulated with other medications that may carry additional risks, such as paracetamol and ibuprofen.

To prevent accidental ingestion in the home pet owners should be mindful of the following:

✅ Keep medicines out of reach of pets. Be extra careful when leaving tablets on bedside tables.

✅ Store human medications separate from pet medications to avoid accidentally mixing them up.

✅ When handling medicines, do so over a table so that if they spill, it’s less likely they will fall on the floor and be subsequently
ingested by your pet.

✅ Never give human medications to a pet unless strictly advised to do so by your veterinarian.

✅ Do not give medicine that has been prescribed for one pet to another.

The Animal Poisons Helpline provides free advice to pet owners in Australia and can be reached on ☎️ 1300 869 738 (AU), 0800 869 738 (NZ) , 3106 4216 (SG), (917) 722-5958 (US) or +1917-722-5958 (CAN). If you are a member of a veterinary team you can join the Animal Poisons Centre For Vets Facebook group which is regularly updated with toxicology tidbits and poisoning trends. To stay up to date with the latest pet poison alerts and receive updates directly to your inbox, visit animalpoisons.com.au/stay-up-to-date and subscribe.