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What is Benadryl Poisoning?

Diphenhydramine is a first-generation antihistamine that is frequently used in the brand-name antihistamine known as Benadryl. Benadryl formulated with just diphenhydramine is a human medicine that can be legally prescribed for extra-label uses for canines as well. It is critical that you check the ingredients on the label as some varieties have additional ingredients such as phenylephrine, which can be dangerous to your pet. It is also important to contact your veterinarian to ensure the proper dosage for your pet, as this can vary somewhat depending on your dog’s health history, size, and other medications.

Benadryl is a well-known brand name utilizing diphenhydramine, one of the earliest antihistamines, and it can be prescribed to dogs to relieve the symptoms of allergy.

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Benadryl Poisoning Average Cost

From 313 quotes ranging from $200 - $500

Average Cost

$250

Symptoms of Benadryl Poisoning in Dogs

Although Benadryl is generally safe for dogs, some side effects can occur. Side effects usually occur within an hour of administration. They are typically mild and can include:

  • Depression
  • Drooling
  • Excitability
  • Lack of appetite
  • Rapid breathing
  • Rapid heart rate
  • Sedation

Overdoses of Benadryl are more often caused by your animal getting a box of the medication from the garbage or medicine cabinet than by being given too much. If you see these signs of an overdose, contact your veterinarian immediately.

  • Abnormal heart rate
  • Aggression
  • Agitation
  • Difficulty breathing
  • Erratic or aggressive behavior
  • Extreme drowsiness
  • Fever
  • Increased blood pressure
  • Muscle tremors
  • Red eyes

Types

Along with a version of diphenhydramine by the name of Vetadryl developed specifically for cats and dogs, there are a few other first generation antihistamines that can be used for dogs. These can include:

Chlorpheniramine

- This antihistamine is frequently used in small animal veterinary practice and is less likely to cause drowsiness than some of the others

Clemastine

- Clemastine is classified as an antipruritic (anti-itch), as well as a sedating antihistamine, and is tends to exhibit fewer side effects

Hydroxyzine

- This drug is a more aggressive antihistamine, but also has more potent side effects 

Meclizine

- Commonly used to reduce nausea, particularly nausea caused by motion sickness

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Causes of Benadryl Poisoning in Dogs

Allergies in canines are the defensive mechanism of the immune system which employs specialized immune cells in the dog’s body to defend it against a substance that it sees as an invader. The specialized cells the body uses to protect itself are known as mast cells, and when the immune system is stimulated by allergens, the mast cells release histamine into animal’s system, which has an inflammatory effect on any tissues that it contacts. This results in the dry, itchy, and inflamed skin conditions characteristic of most allergic reactions in canines. Benadryl, when acting as a remedy for allergies, like other first generation antihistamines, blocks the receptors that the histamine would attach to, thereby stopping the reaction to the histamine. However rare, an allergic reaction to the Benadryl itself is possible.

Toxicity resulting from a large ingestion of a product like Benadryl is caused by the overconsumption of ingredients in the antihistamine. Safe under normal circumstances, the overdose of products that cause effects like drowsiness, muscle tremors, and agitation can be dangerous for your pet, leading to poisoning.

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Diagnosis of Benadryl Poisoning in Dogs

Unless the consumption of the medication was witnessed, the diagnosis of allergic reaction or poisoning is likely to be driven by the symptoms, and supportive treatments will be started as soon as possible. If you see your dog  ingest a large amount of Benadryl, or he seems to be having a reaction to prescribed Benadryl, gather as much information about the incident as possible and provide the details to the veterinary team upon arrival at the clinic. The age and weight of your dog will be measured, and a urinalysis, complete blood count, and biochemistry profile will also be completed at the veterinarian's office at this time as well. 

Currently, there are no reliable tests that can detect the substance in the blood or urine, so the diagnosis is based on symptomatology and timing. It is helpful to have the packaging on hand. The packaging can help determine the strength of the particular type of Benadryl that your pet consumed, as well as ensuring that toxicity from any additional ingredients is addressed before it becomes a problem.

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Treatment of Benadryl Poisoning in Dogs

If you see your dog consume large quantities of Benadryl, but they remain asymptomatic, your veterinarian may instruct you on how to properly induce vomiting. When you reach the veterinarian’s office the treatment of an overdose of Benadryl, or other antihistamines, is mainly supportive. Activated charcoal may be administered to your pet as well in order to soak up as much of the toxin in the stomach as possible and in some cases, a gastric lavage to empty the patient’s stomach, will be initiated. 

IV fluids will most likely be given to prevent dehydration or imbalances in electrolytes, and medications may be given to ease both the tremors and the increased heart rate. It is of particular importance that the temperature is closely monitored so that fevers may be addressed. As overdoses of antihistamines are known to cause a rapid heart rate and increased blood pressure, monitoring the functioning of the cardiovascular system is also critical.

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Recovery of Benadryl Poisoning in Dogs

This medication should not be given to dogs with certain disorders as they may exacerbate them. If your pet has any of these disorders, it is important to let the treating veterinarian know before administering any sort of antihistamine. These disorders may include: 

  • Cardiovascular disease
  • Glaucoma
  • Hyperthyroidism
  • Intestinal atony 
  • Liver disease
  • Pregnancy 
  • Prostatic disease 
  • Urinary retention disorders

Benadryl is also known to react negatively with several types of medication. Alert your pet’s doctor if your dog is taking any sort of other drugs. Medications such as tranquilizers, heparin, epinephrine, or barbiturates are known to interact with diphenhydramine, and can be dangerous when taken in conjunction with Benadryl.

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Benadryl Poisoning Average Cost

From 313 quotes ranging from $200 - $500

Average Cost

$250

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Benadryl Poisoning Questions and Advice from Veterinary Professionals

Need pet health advice? Ask a vet

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Ask a Vet

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Schnauzer

dog-age-icon

6 months

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Unknown severity

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0 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Unknown severity

Has Symptoms

Balance Symptoms And Head To The Side

My daughter's puppy and our other dogs went outside this morning and everyone was feeling well. We feed my son's bassett hound outside and we put his benedry and 1/2 apoquel in his food. When the dogs were coming back in, the puppy couldn't get the door open and was off balance. He is better now (2 hours later) but continues to have balance issues. He is eating okay and drinking water and trying to play. We have an appointment at 2 with the vet but I just wanted to see if it makes sense that perhaps part of the medicine was left uneaten and the puppy got it.

Aug. 7, 2020

Owner

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Dr. Michele K. DVM

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0 Recommendations

Thank you for your question. Depending on the size of the puppy and the dose of the Benadryl, if the puppy got that medication it could cause drowsiness and in coordination. Without knowing those details, it's hard for me to say. It would probably be best for future times to keep an eye on who's getting the medication. I hope it all goes well with your puppy, and that the veterinary appointment goes well and everything is fine.

Aug. 7, 2020

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Golden retriever mix

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One year

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Unknown severity

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1 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Unknown severity

Has Symptoms

Very Nervous

My dog got stung by a bee and his face started swelling up real bad somy neighbor gave him a tablet and a half of Benadryl 25 mg his swelling went down but now he’s acting real nervous running around the house he just started this behavior he was given the Benadryl at around 6:30 PM

Aug. 7, 2020

Owner

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Dr. Michele K. DVM

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0 Recommendations

Thank you for your question. Some dogs have the opposite reaction to Benadryl where it makes them more hyper than sleepy. If your dog seems fine otherwise, you may be fine to keep an eye on him and make sure that he becomes more normal over the next couple of hours. If he continues to have a swollen face or is running around that way, it would be best to have him seen by a veterinarian. I hope that he is okay.

Aug. 7, 2020

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Small Wired haired terrier

dog-age-icon

Six month

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Unknown severity

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0 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Unknown severity

Has Symptoms

None

She ate a Benadryl possibly a 25 mg one

Aug. 1, 2020

Owner

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Dr. Michele K. DVM

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0 Recommendations

Thank you for your question. Unfortunately, without knowing your dogs weight, I'm not sure if that dosage of Benadryl was a problem or not. The safe dose of that medication in dogs is 1 mg per pound, so a 25 pound dog would get 25 mg of Benadryl. If she is much smaller than that, it would be best to call your veterinarian or an emergency clinic and give them the weight of your dog so that they can tell you if you need to worry. I hope that all goes well for your dog.

Aug. 1, 2020

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Husky mix

dog-age-icon

Two Years

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Unknown severity

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1 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Unknown severity

Has Symptoms

Wobbly Can’T Stand Walk

We thought our dog was stung by a bee last night. She had swelling under her eye. We have 25 mg Benedrtyl. It has been 24 hours and now she is very wobbly, can barely stand and cannot walk straight. Slight rapid breathing and confusion. No other symptoms.

July 29, 2020

Owner

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Dr. Michele K. DVM

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Thank you for your question. That does not sound like a typical reaction to a bee sting. It sounds like there may be more going on with her, and it would probably be best to have her seen by a veterinarian. They will be able to examine her, assess her neurologic function and see what is going on, and get an idea as to what treatment might be needed. I hope that all goes well for her.

July 29, 2020

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Doberman Pinscher

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Six Years

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Unknown severity

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0 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Unknown severity

Has Symptoms

Fatigue

My dog is a 6 year old female cross of doberman, blue heeler 70lbs. She was having an allergic reaction. We spoke with the vet and they advised Benadryl was okay and to come in for a shot. After some research we realized that liquid gel was not okay. She had her reaction at 11am yesterday - itchy paws, nose, ears (head shaking). 1pm Sunday- one liquid Benadryl 25mg. 4pm symptoms started- 50mg. 8pm symptoms started and the vet gave he injection of Dexamethasone. 2am 50mg. Now it is 10am Monday and she is not her self. I am worried about the alcohol, in the liquid gel. Have not given her anymor

July 27, 2020

Owner

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Dr. Michele K. DVM

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0 Recommendations

Thank you for your question. I'm sorry that she is not herself. I would be less concerned with the alcohol in the liquid form of Benadryl than her ongoing reaction. Her dose of Benadryl would be about 70 mg, so the beginning doses seemed quite low from what I can tell in your description. Sometimes, reactions will last for longer than the Benadryl or steroid injection does, and repeated therapy is sometimes needed. The best thing to do at this point would probably be to call your veterinarian, let them know what is going on, and get their advice as far as medication that she may need to take in the short-term. I hope that all goes well for her.

July 27, 2020

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Molly

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German Shepard/Labrador

dog-age-icon

9 Months

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Mild severity

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0 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Mild severity

Has Symptoms

Itching
Severe Itching
Minor Lethargy

Been giving our pups benadryl for seasonal allergies and tonight woke up to Molly going nuts trying to scratch her face on anything and everything. She's already in a cone for this exact thing. She always gets about a half dose as she's somewhere between 45-50 lbs. Tonight is the first time she's been given a full dosage. Is there anything to worry about with her age? Or that extra five mg if I'm off on her weight? Just have to be sure.

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Bella

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Pit bull

dog-age-icon

2 Years

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Fair severity

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1 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Fair severity

Has Symptoms

Tired

My dog normally gets 3- 25mg of Benadryl before she goes to bed. However, due to lack of communication she was given 2 more. Therefore had a total of 5-mg tonight before bed. That is a 125mg for a 60lb dog. Is she going to be okay!?

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Ragnar

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Rottweiler

dog-age-icon

6 Years

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Serious severity

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0 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Serious severity

Has Symptoms

Raw Weepy Eyes, Bald Red Spots,

Ragnar has been dealing with what we think are allergies for a long time. He has terribly weepy eyes and hairless spots that are red sometimes. We have been told by some to give Benadryl, 1mg per # twice a day. This would equal to 4+ pills as they are 25mg per pill and he is 110+ lbs. Yesterday I was told by a very dominant person that I was probably poisoning him by giving him so much. He said he only takes one himself and he weighs more than Ragnar. He said I need to give 1-2 a day and it should be plenty and that he works with animals all the time. Also said that no vet would say to give that much. I believe that the dosage we have used is exactly what the vet said 2 years ago. I need a confirmation that we are doing the right thing for Ragnar.

dog-name-icon

Holly

dog-breed-icon

Beagle

dog-age-icon

11 Years

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Moderate severity

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0 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Moderate severity

Has Symptoms

Seizure

My 11 year old beagle had a grand mal seizure 2 days ago. We rushed her to the vet where she was put on oxygen. The vet said that since this was her 1st known seizure we should just keep a journal and if she had 2 more then they would treat her with meds. The only thing different to her routine was that she had her vaccines a week before. Looking back they gave her 50 mg of Benadryl (she weighs 37 lbs), 2 mg of Dexamethasone, DHPP Booster and Rabies 3 yr booster. Could these have triggered her seizure? She's also on Nexguard and Sentinel.

dog-name-icon

Ace

dog-breed-icon

Pit bull

dog-age-icon

1 Year

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Mild severity

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0 found helpful

pill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filledpill-rating-filled

Mild severity

Has Symptoms

Discomfort

I gave Ace 1 25mg tablet of Benadryl, he has separated himself from me and he’s just acting kinda off. This is his first ime taking Benadryl, he’s having an allergic reaction to these treats for dog breath. I haven’t weighed him, but i would say he’s a good 60-70lbs

Benadryl Poisoning Average Cost

From 313 quotes ranging from $200 - $500

Average Cost

$250

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