Is Benadryl for Dogs Really Safe? The Costly Truth

Does your dog suffer from red eyes, itching, and sneezing? Has your vet suggested you give your pup a bit of Benadryl to help suppress the allergy symptoms? Have you tried it? Ever wonder if using Benadryl to try to control your dog’s allergies is a cost savings or if it’s more of a dangerous wire act? This is a story with a personal experience. One that may surprise you as much as it did me. Today let’s dig and discover if Benadryl for dogs cost too much. 

drowsy dog sleeps after having Benadryl For Dogs
disclaimer note
Budget tip:

While it’s always a good idea to try to cut your dog's expenses, there's also a balance to keep in mind with your dog's care. Sometimes we do find something we think works and do it without even thinking. We take advice and then follow it because it appears to be working. We get a bit lazy and don’t pay much attention. That lack of attention can be a fatal flaw. For me, I’ve discovered that I’d rather Henry have itchy or have red and gooey eyes than to fight for his life. I dropped the ball and became complacent in thinking something was working. That was worry. We always need to pay attention to our fur kids, even when it’s something mundane like giving an OTC allergy medicine we’ve administered 100 times. That can save your pup’s life and a vet visit. It’s a win-win to always be awake behind the furry wheel.

What is Benadryl for dogs used for anyhow? 

While the medical name for Benadryl is Diphenhydramine, it’s a basic antihistamine. It can help suppress the symptoms of allergies. My dog, Henry’s vet prescribed Benadryl about five years ago. I have given him 1/2 of a 25 mg pill periodically as his eyes became red, itchy, or gooey. This was more of an issue after he was attacked by a couple of large dogs a few years ago and nearly lost one eye. As part of that attack, his tear duct was crushed in his left eye. Thus, he isn’t as able to flush out foreign objects. 

Basically, Benadryl for dogs works the same as it does for humans. It can treat a multitude of mild allergies by providing temporary relief. These allergy symptoms can include:

  • Seasonal allergies
  • Insect bite
  • Skin allergies
  • Itchy skin (due to mild allergies)
  • Watery eyes (which is what I used it for Henry)
  • Environmental allergies

Does Benadryl work for dog allergies?

It will depend on your dog. Henry’s allergies always seemed to improve each time I gave him a dose. Although, I never gave it to him very often. Maybe once every 3 months and then he’d get a dose once a day for about 3 days. Generally speaking within that timeframe he’d be back to his normal self. He’s been almost like clockwork. 

Wonder if allergy tests for dogs work? Check out this article to find out It was surprising to me as well! 

How much Benadryl for dogs is usually prescribed?

Vets base the amount of Benadryl they prescribe on the weight of a dog. The formula used to calculate the amount of Benadryl is typically 0.9 to 1.8 mg for each pound of a dog’s weight. 

Since Henry weighs 13.8 pounds his vet suggested I give him 1/2 of a 25 mg Benadryl 1-2x/day as needed. However, I would only give him 1/2 once a day as needed. I never wanted to take the chance of overdosing him. Plus, he always seemed to do well on this lower amount. 

Frustrated with your vet? Here’s an article on the 15 Red Flags when it’s time to get a new vet. 

Is there a best time to give Benadryl to my dog?

Generally, vets will say to administer, Benadryl to your dog as symptoms dictate. Your vet will know the correct dosage for your dog and how often you will want to give it to him/her. That could mean your dog’s symptoms require treatment on the weekend or after hours. However, after my experience recently with Henry, my thoughts have changed a bit. Now, I would personally recommend always giving such a drug when you can easily get your dog to veterinary care if it’s required. This may mean treating your dog early in the morning and during the week. I would try to avoid the weekends and late nights if at all possible.

Don’t know how to find a good vet? This article walks you through how to find the best vet for you and your dog

Could my dog do well with Benadryl and then suddenly develop side effects?

Yes! This is what happened to Henry and the severe allergic reaction or side effects that hit him came on very suddenly. And, they were very scary! 

What are the potential side effects of Benadryl for dogs?

Your dog may have any number of potential side effects from Benadryl. Or your dog may not have any side effect symptoms from the medication. However, you will want to look for these potential side effects: 

  • Drowsiness (which often is seen as a good thing to calm a dog. I’ve never used it for hoping for reaction though)
  • Lethargy
  • Unwilling to drink 
  • No appetite
  • Vomiting

Or there could be a severe allergic reaction, which is what happened to Henry.

Within 15 minutes of giving Henry a dose of Benadryl, he suddenly was experiencing symptoms with

  • Walking
  • Sitting
  • Falling over
  • Breathing difficulty

As I said, it was very scary!

What should I do if my pup has a sudden severe allergic reaction to Benadryl for dogs?

When Henry suddenly had this reaction to Benadryl, it took me by surprise. As I looked at him and called his veterinary medicine clinic, he was getting worse with each passing minute. His vet was in surgery for at least 2 hours more hours. I was unwilling to wait since his symptoms were progressing so quickly. So, I called his first emergency vet (he has two) and was put on hold. With no time to wait, I grabbed Henry and rushed to the emergency veterinary clinic 20 minutes away. While a family member drove, I called the vet clinic. They said to rush in, which was also a no-brainer. 

As we drove, I kept reaching around and putting my hands on Henry. I couldn’t feel any breathing. I patted him and said, “Breathe Henry! Breathe, baby!” That seemed to bring a very small breath to his little body. 

Arriving at the vet clinic…

We arrived at the vet clinic. Henry looked up and I carried him into the waiting room. A vet tech came out within minutes and evaluated Henry. With this evaluation, Henry was moved up to a “same day” vet appointment rather than an emergency appointment. This saved me some money. Within minutes we were in an examination room. The vet came in and determined that Henry had a severe allergic reaction to the Benadryl. However, he was certain Henry would pull through as he was starting to regain some alertness. 

Learn how to prepare for an emergency vet visit in this article. 

I asked about pumping his stomach. The vet informed me that within 30 minutes the medication was already in his kidneys and any damage would’ve been done. So, it wouldn’t do any good, but cause more discomfort for Henry. It was decided to give Henry some fluids and keep a watchful eye on him.

By that evening, about 12 hours later, Henry was back to his normal self and I was able to fully breathe. 

Worried about the unexpected emergency vet visit costs? Here’s an article on how to save with an emergency dog fund. 

What else could I have done for Henry?

If I was thinking, I could’ve also called the pet poison hotline. They could’ve directed me on what to do or eased my mind. But honestly, it was most helpful to have a vet’s eyes on Henry and know that he’d be fine. 

Could there be another cause for Henry’s symptoms?

Of course. Nothing is absolute. However, when he was back to his regular self within the timeframe that the medication would take to cycle through his body, it was a good indication that it was the culprit. But you never know there could be some underlying cause or combo of issues at play. But honestly, I’m really hoping that there isn’t. 

Will I use other OTC allergy drugs for Henry?

Since this incident with Henry, he’s been to see his regular vet for his semi-annual checkup. His vet concurred that Henry has developed a severe allergic reaction to Benadryl. He did suggest I could use a different OTC allergy drug for him, like Claritin. But honestly, I can’t deal with the possible side effects. If Henry’s allergy symptoms get extreme then, I’ll consider a different alternative. Perhaps a prescription allergy drug treatment. 

Henry visits his regular vet after a severe reaction to Benadryl For Dogs
Henry’s look of disappointment at having to see his regular vet after his Benadryl incident.

Is the cost of your dog’s prescription meds too much? Here’s an article on how to safely save on your pup’s RX

Is it possible for my dog to die from severe allergic reactions or side effects of Benadryl?

Actually, yes! If your dog gets too much Benadryl or has a very severe allergic reaction it could be fatal. That’s not a risk I’m willing to take. 

How much did I save with Benadryl for Henry – or did I?

I know you’re curious what the breakdown of the Benadryl costs or savings for Henry over the years. Here are the nuts and bolts of it all:

Cost of Benadryl (approx. 3 bottles over 5 years – $5.25 x 3)$15.75
Same-day Emergency vet visit$147.00
Losing Henry??????IMMEASURABLE

It may be different for you and your dog. The point is to be aware that just because something is working today, it may not be tomorrow. So, always pay attention. 

NOTE: I’ve now added Henry’s severe Benadryl allergy to all his tags, micro chip information, and highlighted with his vet records. Thanks to a kind reader for bringing this to my attention. If your dog is allergic to Benadryl or anything it’s a great idea to mark it for your pup as well in the same manner.

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Summary of can Benadryl for dogs cost too much

Honestly, most of the time, Benadryl will do exactly what it’s supposed to do and suppress your dog’s allergy symptoms. But it’s that one time when you mindless give your dog a dose that it could go sideways. For me, I will never give another allergy medication to Henry. I will also make sure that whatever medications I give him I do during office hours, if at all possible. 

Why would a drug Henry’s taken for years suddenly have such a severe reaction? I asked both the emergency (same-day) vet and his regular vet. Both had no idea but both concluded it was the Benadryl and to avoid the drug at all costs. Of course, that was a no-brainer. 

a cute husky rest after receiving Benadryl For Dogs

Has your dog ever had a severe reaction to medication? What did you do? 

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About Terri Rodefer

Terri Rodefer is the founder of Tail Wag Wisdom, a blog focused on affordable pet care. She likes to say helping pet parents afford and love their animals even more, makes her tail wag. As a lifelong lover of all animals with a background in economics, biology, and marketing, allows Terri to bring a unique spin to pet care. 

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