Is Benadryl safe for dogs?

January 24, 2023
Alternative Medicines
dogs Benadryl

Is it okay to give your dogs Benadryl when they’re sick? Read on…

When our pup is feeling a bit under the weather, we want to do anything to make him feel a little better.

However, if you don’t have any medicine for dogs nearby, what are you supposed to do? Wait, what about that stuff you saw in the medicine cabinet called Benadryl…

Is that okay for dogs to have? Or should you avoid giving Benadryl to your dogs?

Well, in this blog we’ll tell you more about whether or not it’s okay to give your dogs Benadryl when they’re sick!

Facts about giving Benadryl to dogs

  • Benadryl is generally safe to give dogs as long as the proper dosage and frequency of giving it to them is followed
  • Benadryl can cause a number of unpleasant side effects, so dog owners should be aware and careful when giving their dogs Benadryl
  • Benadryl can have negative interactions with a variety of different medications, so be sure to let your veterinarian know if you’re giving your dog Benadryl while they’re on other medications

What is Benadryl?


Dosage of Benadryl is based on the weight of the dog and ONLY under the guidance of a vet.

Benadryl is the brand name for antihistamine medication which is used to treat symptoms of allergies, as well as insomnia, anxiety, and motion sickness. It is available in a variety of forms, including tablets, capsules, topicals, and liquid. Benadryl for dogs is typically dosed based on the weight of the dog, with a usual range of 1-2 mg/pound given every 8-12 hours.

What does Benadryl treat in dogs?

Benadryl can be used to treat a variety of conditions in dogs, including allergies, motion sickness, anxiety, and insomnia. Most commonly, Benadryl is used to help alleviate allergies in dogs which include itching, sneezing, and scratching. Benadryl is also used to treat a number of other conditions like anxiety and insomnia because of its ability to slow the heart rate and make it feel easier to breathe. However, Benadryl should only be given to dogs under the guidance of a veterinarian, as the correct dosage and frequency of use will be different for each dog.

How does Benadryl work?

Benadryl For Dogs

The active ingredients of Benadryl slow the heart rate and make it feel easier to breathe.

Benadryl’s active ingredient – diphenhydramine – blocks the action of histamine: a chemical produced by the body in response to certain stimuli. When histamine is released, it binds to different receptors throughout the body – known as H1, H2, and H3 receptors  – which can cause a host of different symptoms.

H1 receptors are primarily found in the respiratory tract, skin, and blood vessels. When the histamine binds to H1 receptors, this causes the blood vessels to dilate and become more permeable. What follows for your pup is a swelling, inflammation, and overstimulation of the respiratory tract. Once this happens, he/she typically reacts by sneezing, coughing, and experiencing difficulty breathing. Benadryl or any antihistamine slows or stops this process.

H2 and H3 receptors are primarily found in the stomach and brain. When histamine binds to these receptors, it can lead to an elevated heart rate, increased blood pressure, and the increased release of neurotransmitters. As a result, this can make your canine feel much more alert, nervous, or anxious. Less is understood about the role that H4 receptors play in the body, or what symptoms they directly cause in dogs. Again, Benadryl or any antihistamine slows or stops this process.

Benadryl, as an anti-histamine, works by binding to these different receptors before histamine has the chance to interfere and cause problems. By binding to these receptors first, antihistamine medications prevent histamine from triggering the unpleasant bodily reactions noted above.

Is Benadryl Safe for Dogs?

Vet Giving Dog Benadryl

Give the correct dosage and frequently monitor for adverse reactions.

Generally speaking, Benadryl is safe for dogs to consume if given as long as the correct dosage is given. However, there are still a number of precautions that pet parents need to take before giving their dog benadryl.

As with any new medication, always observe your dog closely after administration to make sure there aren’t any adverse reactions. If you have any further questions about Benadryl for dogs, contact your veterinarian for more information. And remember to keep all medicines out of reach of your curious canine pal.

When should you give a dog Benadryl?

Benadryl may be a good option for dogs experiencing mild to moderate symptoms of conditions that don’t require more aggressive treatment. It is important to keep in mind that the correct dosage and frequency of use of Benadryl will depend on the specific condition being treated, as well as the individual dog’s characteristics and underlying health conditions.

If a dog is experiencing more severe symptoms or has a more serious condition, a different medication may be more appropriate. If you have concerns about which medication is best for your dog, it is important to consult with a veterinarian for guidance

Side effects of Benadryl for Dogs

Benadryl can cause a number of side effects that dog owners should be aware of. These side effects will typically present within the first three hours after being administered, so it’s important to keep a close eye on your dog during this time. Some of the typical side effects of Benadryl for dogs include:

  • Drowsiness
  • Dry mouth
  • Urinary retention
  • Hypersalivation
  • Increased heart rate
  • Rapid breathing
dog hives

Swelling of the face is one of the rare side effects.

In some rare instances, Benadryl can produce slightly more severe side effects in dogs. Rare side effects of Benadryl for dogs include:

  • Red rashes on the skin
  • Swelling of the face or tongue
  • Vomiting or diarrhea
  • Changes in appetite
  • Skin chewing or licking

If you notice your dog is displaying any of these symptoms, call your veterinarian immediately. These symptoms can be signs that your dog is having an allergic reaction to the active ingredient in Benadryl.

Benadryl overdose in dogs

Unfortunately, it is possible for a dog to overdose on Benadryl if they are given too much of the medication or if they are given the medication too frequently. An overdose on Benadryl can cause a variety of scary and dangerous side effects. Symptoms of Benadryl overdose in dogs include:

  • Rapid heartbeat
  • Dilated pupils
  • Agitated behavior
  • Slowing breathing
  • Tremors or seizures
  • Coma

If you suspect your dog overdosed on Benadryl, seek veterinary care immediately so your vet can assess your dog’s condition and determine a course of treatment. They may recommend medications to counter the effects of the overdose, such as activated charcoal to absorb the medication or medications to reverse the sedative effects of the Benadryl. In severe cases, hospitalization may be necessary.

Canine medication interactions with Benadryl

diphenhydramine for dogs

Mixing medications can cause unwanted side effects… even death!!!

Benadryl can cause several unwanted side effects if taken in conjunction with some medications that are used to treat chronic disorders or illness in dogs.

Glaucoma medication for dogs (carbonic anhydrase inhibitors):

Carbonic anhydrase inhibitors are a type of medication that inhibit the action of an enzyme called carbonic anhydrase. This helps regulate the balance of fluids in the body to reduce pressure in the eye, control seizures, and prevent altitude sickness.

If Benadryl is taken with this medication, it can cause excessive drowsiness and impaired cognitive function. In rare cases, this combination can cause a serious and potentially deadly reaction called serotonin syndrome.  This can cause symptoms such as confusion, agitation, hallucinations, fever, and rapid changes in blood pressure.

High blood pressure medication for dogs (beta-adrenergic blocking agents):

Beta-adrenergic blocking agents, also known as beta blockers, are a class of medications that are used to treat various conditions, including high blood pressure, angina (chest pain), and heart failure. Beta blockers work by blocking the effects of the hormone epinephrine, also known as adrenaline, on the heart and blood vessels. This can help to lower blood pressure and reduce the risk of heart attacks and other cardiac events.

When a dog takes Benadryl and beta blockers together, the combination of these medications can increase the risk of drowsiness and potentially dangerous slowing of the heart rate.

In addition, Benadryl can cause dry mouth and constipation, while beta blockers reduce blood flow to the legs and arms. These effects may be more pronounced when the medications are taken together.

Seizure medication for dogs (phenobarbital):

Phenobarbital is a barbiturate that is used as an anticonvulsant to treat seizure disorders in dogs. It works by slowing down the activity of the central nervous system. When a dog is given both Benadryl and phenobarbital, the sedative effects of both medications can be more pronounced. This could cause the dog to be more drowsy or lethargic than usual.

Another potential interaction is an increase in the risk of respiratory depression. Respiratory depression is a condition in which the respiratory/breathing system becomes less efficient.  This can lead to a risky decrease in oxygen levels in the body. Both Benadryl and phenobarbital can cause respiratory depression on their own, so the risk is much higher when the two are given in conjunction with one another.

Monoamine oxidase inhibitors (MAOIs) and Tricyclic antidepressants (TCAs):

MAOIs and TCAs are antidepressant medications that inhibit enzymes from breaking down dopamine, serotonin, and norepinephrine. By inhibiting the action of these enzymes, these medications can increase the levels of these neurotransmitters and help to improve mood.

When taken with MAOIs or TCAs, Benadryl can increase the sedative effects of these medications, leading to increased drowsiness and impaired cognitive function. In rare cases, the combination of diphenhydramine and MAOIs can also cause serotonin syndrome.

Opioid pain medications:

Opioid pain medications, such as morphine and oxycodone, work by binding to opioid receptors in the brain and spinal cord, which can reduce the perception of pain and produce a feeling of euphoria. These medications can be effective at relieving pain, but they can also cause sedation and impaired cognitive function.

If taken alongside opioids, Benadryl can increase its sedative effects and cause excessive drowsiness and impaired cognitive function. This can be dangerous, especially if the dog is also experiencing pain. It may make it more difficult for them to respond to their surroundings or lower their ability to breathe.

Be sure to communicate with your Veterinarian re your dog’s meds

veteranarian benadryl and other medicine

Always consult with your vet when before giving dog meds.

If you are giving your dog Benadryl and they are taking any of these medications, please inform your veterinarian. Even though your Vet may be the person who has prescribed the medications, Don’t Expect them to remember.  Be an advocate for your dog! Your veterinarian may then need to adjust the dosages of the medications or, recommend an alternative treatment.

Spotting a negative Benadryl reaction in your dog

To spot whether a negative interaction is occurring, keep an eye out for lethargy, difficulty waking up, stumbling or loss of coordination, and/or problems breathing. If your dog presents with any of these, contact your veterinarian immediately.  These can be signs of excessive drowsiness or sedation.

Of course, you already know to be cautious when it comes to your pet’s health – otherwise you wouldn’t be reading this blog! That’s why we hope you’ll come back to our blog to learn more about how to keep your four-legged friend happy and healthy.  If on the other hand, you are interested in how to maintain your dog’s nails/claws, we cover that too.  Interested in more quirky items such as how long can a dog go without peeing, yep, we’ve got that covered.


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