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Dr. B.
Dr. B., Veterinarian
Category: Dog Veterinary
Satisfied Customers: 21419
Experience:  Hello, I am a small animal veterinarian and am happy to discuss any concerns & questions you have on any species.
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My dog ate a piece of onion around 6 hours ago. I woke up

Customer Question

My dog ate a piece of onion around 6 hours ago. I woke up and he is covered in hives and really itchy
Submitted: 2 years ago.
Category: Dog Veterinary
Expert:  Dr. B. replied 2 years ago.

Hello, I am afraid that the expert you have requested is not currently available. Still I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.

How much onion did he have? Anything else?

How much does he weigh?

Are his gums pink or pale?

Any issues with his breathing?

How much Benadryl did you give?

Customer: replied 2 years ago.
Just a small cut up piece. He is about 65lbs. Gums are pink, breathing is normal. I gave 25mg of Benadryl
Expert:  Dr. B. replied 2 years ago.

Thank you,

First I have to note that none of the signs we are seeing fit with onion ingestion. If he is that large and it was just a small piece, we'd not actually expect any signs from that. If he had eaten more, then mild signs usually focus on GI upset (appetite loss, vomiting, diarrhea). And in severe ingestions, we can see anemia which can cause lethargy, breathing issues and collapse. So, as you can see this obvious allergic reaction doesn't fit with having eaten an onion at all.

With that in mind, I would advise looking around the house for another potential item he may have eaten. As well, we need to properly tackle that allergic reaction. Now the dose you have is only 0.86mg/kg. This is less then the therapeutic dose for his weight and we'd not expect that to help much at all. Instead, he needs a dose of at least 29mg but can safely have up to 118mg. Therefore, at this point, I'd advise giving at least another 25 mg just now. And plan to give at least 50mg every 8 hours for the next 24 hours. Of course, do be aware it can make them drowsy and we need to check with his vet first if he has any known health issues or is on other medications. And I would also note that if the hives do not settle even with higher doses, then we'd need to consider seeing his vet so that injectable steroids can be used to break this allergic reaction.

Overall, these signs are telling us he is reacting to something but onions aren't likely the cause. So, do just tread with care and keep an eye out for anything else he may have gotten into (just in case it can cause other issues). Otherwise, do adjust that Benadryl dose for his weight so that we can and halt the reaction. But if he isn't settling even with a proper dose, then steroids from his vet would be indicated.

I hope this information is helpful.

If you need any additional information, do not hesitate to ask!

All the best,

Dr. B.


If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need as this is how I am credited for assisting you today.Thank you! : )

Expert:  Dr. B. replied 2 years ago.
Hi Samantha,
I'm just following up on our conversation about Louie. How is everything going?