Medicines
Is antihistamines toxic to cats and dogs?
Also sold as Benadryl, diphenhydramine, cetirizine (Zyrtec), loratadine (Claritin), hay fever tablets
Cats
ToxicDogs
ToxicVets sometimes prescribe antihistamines for pets, but an overdose can cause agitation, a racing heart and seizures. Combination products with a decongestant — often marked "D" — are far more dangerous.
By Maya HartIf your pet got into it
- Call your vet or a pet poison helpline now, even if your pet seems fine.
- Have the packet ready: the vet needs the name, strength and how much may be missing.
- Do not make your pet sick unless a vet tells you to.
- Check the packet for a decongestant: names ending in "-D" or containing pseudoephedrine are an emergency.
Signs to watch for
- Sleepiness or, often, agitation and hyperactivity
- Racing heart
- Dilated pupils
- Dry mouth, vomiting
- Tremors and seizures (large doses or decongestants)
How much is dangerous
Depends on the drug. Overdoses well above the vet-prescribed dose cause signs; a single decongestant combination tablet can poison a small dog.
Keeping it safe
- Only give an antihistamine at the dose your vet gives you for your pet’s weight
- Never use combination cold-and-allergy products
- Check liquid formulations for xylitol
The details
Antihistamines are one of the few human medicines vets sometimes use in pets, which leads many owners to give them without advice. The safe dose depends on the drug and the animal’s weight, and many products sold in pharmacies combine an antihistamine with a decongestant such as pseudoephedrine — a stimulant that can cause dangerous heart rhythms and seizures in dogs and cats.
For itchy pets, modern veterinary anti-itch medicines work far better than antihistamines in most cases.
Questions owners ask
Is antihistamines toxic to cats?
Yes — toxic.
Is antihistamines toxic to dogs?
Yes — toxic.
How much is dangerous?
Depends on the drug. Overdoses well above the vet-prescribed dose cause signs; a single decongestant combination tablet can poison a small dog.
What should I do if my pet got into it?
Call your vet or a pet poison helpline now, even if your pet seems fine. Have the packet ready: the vet needs the name, strength and how much may be missing. Do not make your pet sick unless a vet tells you to. Check the packet for a decongestant: names ending in "-D" or containing pseudoephedrine are an emergency.
Sources
Tailwise is for general information and is reviewed by veterinary professionals, but it is not a substitute for advice from your own vet, who knows your pet. How we check facts