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Benadryl for Dogs

Benadryl is a brand name for diphenhydramine hydrochloride, which belongs to a group of antihistamines and is primarily used to treat allergy symptoms. It is human medication, but veterinarians use it regularly to treat allergy symptoms, as well as nausea, motion sickness, and anxiety in dogs.

Antihistamines, like Benadryl, work by reducing the action of histamine, which is released by immune cells and is responsible for the signs of inflammation. In addition to its effects on allergies, antihistamines also have anti-anxiety, sedative (calming) effects. Keep reading to find out if Benadryl is safe for all dogs, what the appropriate dose is, whether it is better to use liquid Benadryl or Benadryl tablets, and everything else you need to know about using this medicine in dogs.

Is Benadryl Safe for Dogs?

Although Benadryl is not yet FDA-approved for veterinary use, veterinarians across the U.S. use it because it is considered to be safe for dogs if given in appropriate doses. However, each dog is an individual organism and the same rules do not apply to everyone. That is why Benadryl should not be used in treatment of dogs that have certain health issues, such as the following:

  • High blood pressure
  • Glaucoma
  • Diabetes
  • Heart disease
  • Seizures or epilepsy
  • Hyperthyroidism
  • Pregnancy
  • Urinary tract problems
  • Health problems in dogs that cause vomiting, because it can worsen their current condition

It is also advisable to avoid giving Benadryl to dogs that are lighter than 13 pounds, as you can very easily overdose them and cause side effects, and do not give it to pregnant females to avoid adverse effects on the fetus.

Puppies don’t have a developed metabolism that can break down and resorb drugs in the same way as an adult dog’s organism, so you also need to pay attention and consult a veterinarian before giving Benadryl to puppies.

It is important to say that blocking the H1 (histamine) receptors means suppressing the body’s natural response, so Benadryl’s usage should be a short-term solution because it can be a double-edged sword.

In addition to Benadryl, other human drugs, such as Zyrtec, Xanax, Klonopin, and Desyrel are sometimes used to calm and treat certain health issues in dogs, such as allergies, seizures, separation anxiety, storm anxiety, motion sickness, and behavior problems. However, they contain substances such as cetirizine, alprazolam, clonazepam, gabapentin, tramadol and trazodone, so it is not recommended to use them in combination with diphenhydramine (Benadryl), because they can lead to side effects on your dog’s health.

In addition to Benadryl, there are other brands that sell medicine based on diphenhydramine, and they may contain other substances in their composition, such as xylitol, acetaminophen, and pseudoephedrine. These substances are toxic for dogs, so you should definitely check the ingredients of the medicine or consult a veterinarian about the choice of medicines you intend to give your dog.

Generally speaking, Benadryl is safe to use when properly dosed, but you should consult your veterinarian before introducing it to your dog’s treatment.

Benadryl for Dog Anxiety

Antihistamines, like diphenhydramine, the main active ingredient in Benadryl, also have a relaxing effect, which is why Benadryl is sometimes given to dogs in situations where they suffer from separation anxiety, storm-induced anxiety, or insomnia. Due to its sedative effect, it is applicable in situations where there is a risk that your pet will be exposed to a high dose of stress, such as during a long car trip, before flying, or when the dog is exposed to loud and sudden noises (during fireworks, etc.).

However, if a dog uses Benadryl for therapeutic purposes on a daily basis, the sedative effect may decline over time and disappear completely. This means that some dogs can become resistant to this medicine if you give it to them too often, so you should not overdo it or use it for every little thing.

Benadryl for Dog Allergies

Allergic reactions in dogs most often occur due to hypersensitivity or intolerance to a certain food, sensitivity to environmental allergens (dust, mites, pollen, insect bites), skin and hair products, medications, and vaccines. Discovering the type of allergy, its treatment, and the choice of medication requires special dedication and attention. Benadryl is good at relieving skin irritation, redness, pruritus, and urticaria, as well as allergic rhinitis.

It can be used in heartworm treatment and for treatment of flea irritation, as well as for insect and snake bites. It is important to emphasize that Benadryl doesn’t treat the snake bite itself (the only treatment for that is antivenom), but it helps to manage allergic reactions.

In addition to allergies and anxiety, Benadryl also helps in soothing cold symptoms and extrapyramidal symptoms (movement disorders). It can also be given to dogs for preventing nausea that occurs due to motion sickness, and in dogs suffering from a vestibular disease (eustachian tube dysfunction).

However, since Benadryl is a human medicine and it is not approved by the FDA for the treatment of dogs, it is advisable to consult a veterinarian if you want to include it in the treatment of your dog in order to safely determine the appropriate dose.

Benadryl Dosage for Dogs – How Much Benadryl Is Safe for a Dog?

The right dosage of Benadryl depends on the weight of the dog. The maximum daily dose used for therapeutic purposes for dogs is 1 milligram per one pound of body weight every 8-12 hours (two to three times a day).

The tablets are recommended to be given with food or treats, as the dog would rather take them that way and he will not even notice that he has eaten them.

Since each dog reacts individually to different types of therapy, it is best to consult your veterinarian before giving any medication to your dog. Dogs with hormonal disorders, prostatic hypertrophy, seizures, heart and urinary tract issues, breathing problems, keratoconjunctivitis sicca, glaucoma and pregnant females are at risk of deteriorating their current health if exposed to Benadryl.

Giving Benadryl tablets is not recommended for smaller dogs (lighter than 13 pounds) because there is a risk of overdose, so it is better to give them liquid Benadryl.

Liquid Benadryl for Dogs

Liquid Benadryl is a better choice when we want to give this medicine to dogs because it is easier to dose. Liquid Benadryl is best given to a dog with wet food, but if you decide to apply it with a dropper, after squeezing the medicine from the side of the lips into the dog’s mouth, give him a treat to make him forget that he swallowed the medicine.

Some formulas of Benadryl and similar products from other brands may contain alcohol, which is toxic to dogs, so when buying this medicine, it is good to check the ingredients or simply get a version of Benadryl for children since children’s products do not contain alcohol.

Children’s Benadryl for Dogs

Children’s liquid formula of Benadryl is safer for use in dogs. It doesn’t contain alcohol, artificial colors, or sweeteners, and it’s very practical for dosing. You can use a syringe or teaspoon when giving your dog liquid Benadryl.

Please do not determine the dose for your dog on your own, and do not follow the doses that are recommended for children. It’s always good to consult your veterinarian before administration of Benadryl to your dog in order to determine the appropriate dose.

Liquid Benadryl Dosage for Dogs

As previously mentioned, liquid Benadryl is easier to dose. The recommended doses per weight of the dog are as follows:

  • 5 – 10 lbs = 2 – 4 mL
  • 11 – 20 lbs = 4 – 8 mL
  • 21 – 30 lbs = 8 – 12 mL
  • 31 – 40 lbs = 12 – 16 mL
  • 51 – 60 lbs = 20 – 24 mL
  • 61 – 70 lbs = 24 – 28 mL
  • 71 – 80 lbs = 28 – 32 mL
  • 81 – 90 lbs = 32 – 36 mL
  • 91 – 100 lbs = 36 – 40 mL
  • 100+ lbs = 40+ mL

Before giving Benadryl to a dog, it is always better to consult a veterinarian, as determining the appropriate dose for your dog may depend on several factors (such as health status). To ease the administration of this medicine and to increase measurement accuracy, use a syringe.

Side Effects of Benadryl

Benadryl can potentially cause side effects in dogs that are very similar to those that can occur in humans. They most commonly occur due to inappropriate dosing and when combining Benadryl with certain drugs. This can happen more often in puppies and smaller dogs due to it being more difficult to determine dose than in larger dogs.

In some dogs who have a particular allergy, Benadryl may be counterproductive and worsen symptoms, so you need to give a small dose first and monitor your dog’s condition, symptoms, and behavior.

Side effects that can occur when using Benadryl:

  • Dryness of mouth, nose, and throat
  • Drowsiness (sedative effect)
  • Change in appetite (increased or reduced appetite)
  • Hypersalivation
  • Anxiety
  • Nausea
  • Vomiting
  • Diarrhea
  • Constipation
  • Lethargy
  • Trembling
  • Breathing difficulties
  • Increased heart rate
  • Heart palpitations
  • Low blood pressure
  • Urinary retention
  • Cognitive issues, confusion, dementia
  • Moodiness
  • Depression
  • Chemical dependence

Most side effects are not so dangerous to the dog’s health and do not leave consequences, but some of them can cause harm in dogs that already have certain health problems. This is the case with urinary retention, which can cause additional health issues in dogs that have kidney or liver problems. Also, some side effects, such as constipation, can mask existing health problems such as issues with the gastrointestinal tract.

In case any of the above side effects occur, you should contact a veterinarian immediately. You must be very careful when giving Benadryl to your dog so as not to accidentally give him a higher dose than you should. The symptoms that indicate an overdose in a dog include the following:

  • Intense drowsiness
  • Vomiting
  • Dizziness
  • Fever
  • Muscle tremors
  • Red eyes or dilated pupils
  • Acute megacolon
  • Abdominal pain
  • Difficulty urinating
  • Difficulty breathing
  • Rapid heart rate
  • Anxiety
  • Euphoria or dysphoria
  • Aggression
  • Disorientation
  • Lack of coordination, inability to walk
  • Seizures
  • Hallucinations
  • Delirium

The symptoms that occur due to overdose are very serious and can be fatal for your dog. If you suspect that your dog has ingested too much Benadryl, contact your veterinarian or emergency department immediately.

Putting a Dog to Sleep with Benadryl

Some dog owners choose to put their dogs to sleep with Benadryl by giving them a dose that is three to four times higher than the recommended one. Those who have euthanized a dog in this way, or plan to do so, most often mention one of the following two reasons as an explanation for their decision.

The first reason is the lack of money to afford taking their dog to a veterinarian to euthanize the dog in a professional way. The second reason they mention is that they simply want to do it in the privacy of their home because they don’t want their dog to spend their last moments in some unfamiliar room and without their presence.

It’s certainly not easy to watch a dog suffer from sickness or injury; however, putting a dog to sleep with Benadryl is not exactly the most humane decision you can make. It can easily happen that you give the wrong dose and actually make your dog suffer even more. Therefore, it is better to avoid putting the dog to sleep in this way at all costs. Besides that, putting a dog to sleep with Benadryl is an illegal act in some states.

If you are determined in your intention to put a dog to sleep at home, there are veterinarians who are willing to come and euthanize your dog in your home, so consider that option before you decide to do something on your own.


Benadryl is not FDA approved, but veterinarians use it in everyday practice to treat certain health issues in dogs because it is safe if properly dosed. Generally speaking, Benadryl is safe for the treatment of various types of allergies, anxiety, motion sickness and sleep disorders in dogs. For these purposes, it is best to use a liquid formula for children that is safer for dogs since it doesn’t contain alcohol and it is easier to dose.

It usually takes 30 minutes for Benadryl to start working, so keep that in mind if, for example, you plan on using this medication to calm your dog before a stressful event. Most side effects usually occur within the first hour of Benadryl administration, so it is recommended to monitor your dog closely during this period.

Although there are recommended doses per the dog’s weight, which you can learn more about “here,” to avoid side effects or overdose, it is better to consult a veterinarian before giving this medicine to the dog. Weight is not the only determining factor for dosage; it is also necessary to take into account the health status of the dog and any existing medical issues.

For dogs suffering from certain health problems, such as glaucoma, hypothyroidism, etc., Benadryl can cause more harm than good, so it is recommended to avoid its administration in such cases. You can find out more about this in the section “Is Benadryl Safe for Dogs?

In the multitude of information available about Benadryl online, there are some that suggest that this drug can be used for euthanizing a dog at home. It is important to point out that this is not the most humane decision you can make, and you should not do it on your own because you can easily give the wrong dose and make the dog suffer even more. Besides, putting a dog to sleep with Benadryl is illegal in some states.

If your dog is seriously ill or injured and euthanasia is the only solution, but you want him to spend his last moments in a familiar environment, there are veterinarians who are willing to come to your address, so consider that option. This way, you will be sure that you did your best to make the end as painless as possible for your dog.

Frequently Asked Questions (FAQs) About Benadryl for Dogs

Can I Give My Dog Benadryl for Itching?

Yes, you can give Benadryl in cases where your dog has itchy skin (pruritus), and it also works well on other allergy symptoms.

Can I Give My Dog Benadryl for Pain?

Benadryl is an antihistamine that can be used in dogs to reduce and eliminate the signs of inflammation, and one of them is pain. It is necessary to follow the instructions for use and to consult a veterinarian to determine the adequate dose at which Benadryl will be most effective for your dog.

What Does Benadryl Do for Dogs?

Benadryl reduces and eliminates the signs of inflammation (local heat, redness, swelling, and pain) and soothes the symptoms of allergies (skin, seasonal, food allergies, and allergies to certain medications and vaccines). It is also used in the treatment of anxiety, relieving nausea in dogs before travel and in stressful situations, as well as in the treatment of insomnia because it has a mild sedative effect.

How Much Benadryl Can I Give My Dog?

The recommended dose is determined based on the dog's weight, and it is 1 mg per one pound of body weight, two to three times a day. It is recommended to start with half the dose and monitor how your dog will react to the medicine. More information on dosing can be found in the section 'Benadryl Dosage for Dogs - How Much Benadryl Is Safe for a Dog?'

What Kind of Benadryl Is Safe for Dogs?

Benadryl is generally considered safe for dogs, but liquid Benadryl is easier to dose than tablets. Since some formulas of liquid Benadryl may contain alcohol, it is advisable to use a product intended for children, as it does not contain alcohol, which is toxic to dogs.

Can My Dog Overdose on Benadryl?

Yes, your dog can overdose on Benadryl. An overdose of Benadryl causes hyper-excitation of the central nervous system, and the first signs that you have given too much medication to your dog usually occur within an hour. Symptoms indicating an overdose can be found in the 'Side Effects of Benadryl' section.

Which Benadryl Is OK for Dogs?

For the treatment of some forms of allergies, anxiety, and insomnia, and for the prevention of motion sickness for dogs (especially for smaller breeds) the liquid Benadryl for children is appropriate because it is the easiest to dose and does not contain alcohol, which can be fatal for dogs. For larger dogs, the tablet form of Benadryl can also be used.

How to Euthanize a Dog with Benadryl?

Some people decide to euthanize their dog with Benadryl by giving him a three to four times higher dose than recommended. However, this is not the most humane way to euthanize a dog because you can easily apply the wrong dose of medication and make the dog suffer more. Furthermore, putting a dog to sleep with Benadryl is illegal in some states.

How Much Benadryl Does It Take to Euthanize a Dog?

Some dog owners choose to euthanize a dog at home with Benadryl for a variety of reasons, and they do so by giving the dog three times the dose of Benadryl than recommended. However, veterinarians do not recommend this method mainly because it is not humane; it is easy to get the dosage wrong and cause your dog to suffer even more. Also, euthanizing a dog with Benadry has been declared illegal in some states in the U.S.

How Long Does It Take to Euthanize a Dog with Benadryl?

Although euthanizing a dog with Benadryl is an inexpensive method of putting a dog to sleep, it certainly isn't the most humane way because Benadryl is not primarily intended for it. Benadryl is a sedative that works slowly, even when given in large doses. It takes half an hour after applying the euthanasia dose to completely slow down your dog's heart rate and ultimately stop his heartbeat. Prolonged time of cessation of vital organ functions and falling into a coma makes this way of euthanasia inhumane.

How Much Benadryl Is Needed to Cause a Dog to Sleep?

If you want to know what dose of Benadryl is needed to give a dog to fall asleep, the answer is 1 mg per one pound of body weight.

Dr. Elvira Sefo-Kapidzic (DVM)
Dr. Elvira Sefo-Kapidzic (DVM)
Dr. Elvira is working as a field veterinarian and in a small animal ambulance in Sarajevo. She has a deep knowledge of toxicity in dog food. She has successfully completed a large number of seminars in her special fields. She is a proud mom of 11-years old labrador retriever “Bonny”.

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