Benadryl for Dogs: Guide for Dosage, Side Effects and Tips

By Josie F. Turner, Journalist specialized in Animal Welfare. November 15, 2017
Benadryl for Dogs: Guide for Dosage, Side Effects and Tips

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You may have heard of the use of Benadryl for humans, as it is a popular antihistamine medicine. Dogs can also have allergies just like their carers, which is why you shouldn't be alarmed if your pet has been prescribed Benadryl by the vet, as this is one of the only over-the-counter drugs than dogs can take. At AnimalWised we want to give you a complete guide to Benadryl for dogs, so you can learn how to give them the right amount, learn what side effects it has for your pooch and the most frequent questions asked by users.

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When should dogs take benadryl?

Benadryl is the commercial name of diphenhydramine, which is a antihistamine that works by blocking H-1 receptors which are histamine receptors and are in charge of producing the inflammation caused by allergies.

A vet will prescribe benadryl for your dog in different situations, the most common being the following:

  • Relieving symptoms of allergy in dogs: This drug can help reduce the most common symptoms of allergies, including itching, hives, swelling, redness, runny nose and eyes, cough, sneezing, anaphylactic reactions. This is the most common use of Benadryl for dogs. In this sense, it can also be used after a bad reaction to an insect's sting or bite.
  • Mitigating mast cell tumors: Dogs with mas cell tumors have a a great release of hystamine caused by mast cell degranulation. Diphenhydramine or Benadryl can help mitigate the effects of its release.
  • As part of heartworm treatment: This drug can be prescribed by vets occasionaly to prevent the allergic reactions that sometimes accompany this condition.
  • Insomnia: Although melatonin is usually used for sleeping issues in dogs. Benadryl may also be prescribed for this purpose by a vet in particular cases.
  • Travel sickness: Dogs that suffer from motion sickness when travelling can also be prescribed diphenhydramine by a vet, as it is very similar in content to dimenhydrinate.
  • Anxiety: Again, this is not the most prescribed treatment, but in some cases of situations in which a dog suffers from anxiety, a vet may also suggest the use of this drug due to its sedative properties to calm the dog's nerves.

Note that, although it is commonly prescribed by vets, this drug has not yet been approved for veterinary use by the FDA[1].

Can you give a dog Benadryl to calm them down?

As we'll explain in further detail later on, one of Benadryl's side effects is drowsiness, which is why it can calm a dog down and make them sleepy. Many people know about this effect, which is why they think it can be a good remedy to calm a nervous dog down. However, it is not recommended to medicate your dog without your vet's previous consent.

Cases of anxiety in dogs should be treated by your vet, and only in severe cases is any type of medication prescribed.

When not to give your dog Benadryl

It is also important to know in which cases it is not safe to give your dog Benadryl, as it is contraindicated for several conditions:

  • Glaucoma: Although you may think that eye redness in dogs is a symptom of allergy, this can also indicate glaucoma, a condition that can worsen if you give your dog benadryl.
  • Pregnancy: Female dogs that are expecting or are currently breastfeeding should not be given this medicine under any circumstances as it can affect the health of the newborn puppies.
  • When using other drugs: If your dog has been prescribed any other form of anticholinergic drug you should not combine it with diphenhydramine as it can cause toxicity symptoms.
  • Depression: The calming effect of this drug can worsen your dog's depression, especially if they are being medicated for this condition too.
  • Prostate enlargement
  • Hyperthyroidism
Benadryl for Dogs: Guide for Dosage, Side Effects and Tips - When should dogs take benadryl?

How much benadryl should I give a dog?

You should only give a dog Benadryl, and not any of its other products such as "Benadryl sinus" or "Benadryl itch cooling gel" because it can contain ingredients such as xylitol, camphor, Tylenol or alcohol that are bad for your dog. There are different forms of Benadryl and, although you can use them in pills and liquid form, you should never give them time-release capsules (pictured above) due to the dog's body's absorption. Once the vet has indicated the exact medication and you have listened carefully to their instructions, you can proceed to give your dog this medicine, but in the right amount.

The vet should indicate the right amount of Benadryl to give your dog depending on their condition, although recommendations say that you should give your dog from 2 to 4 mg per kilo (1 to 2 mg per pound) your dog weighs. For example, how much Benadryl for a 10 pound dog? The answer is between 10 to 20 mg per dose. It should be given to your dog two to three times daily or every 8 to 12 hours.

In liquid form, it is recommended to give a dog no more than 0.4ml per pound your dog weighs. If your dog weighs 10 pounds, you should give them 4 ml liquid Benadryl.

Benadryl and other forms of diphenhydramine can also be used topically as a local anesthetic to reduce itching in dogs. In this case, using this medicine in cream or gel is also indicated. Apply to the area two to three times a day in this case.

Remember dosage will depend on the form of Benadryl prescribed by your vet and their own condition.

Benadryl for Dogs: Guide for Dosage, Side Effects and Tips - How much benadryl should I give a dog?

How long does benadryl take to work in dogs?

The effects of Benadryl will usually begin 30 minutes after your dog has taken it. When using this medicine to prevent motion sickness, you should give your dog this drug 20 minutes before the journey begins.

Gels will need to be left on the dog for 10 minutes if you are applying it while bathing your dog with shampoo for perfect results.

Side effects of benadryl in dogs

Apart from the contraindications mentioned above, even if your dog does not have any of those conditions, Benadryl has certain side effects that can manifest in your dog.

You may commonly notice your dog behaving in a strange manner, with slow reflexes. This is because the most common side effects of Benadryl are:

  • Drowsiness and sleepiness
  • Dry mouth (you will notice your dog wants to drink lots of water)
  • Urinary retention
  • Sluggish or slow reactions

There are also less common symptoms that can occur in your dog but that can also be observed if you have given your dog Benadryl:

  • Diarrhea
  • Vomiting
  • Lack of appetite
  • Allergy (you should take your dog to the vet immediately if you notice symptoms of allergy)

Giving your dog a higher dose than what has been prescribed can put them in danger. If you have accidentally given your dog a higher dose you should take them to the vet immediately, especially if you notice the following symptoms:

  • Tremors
  • Rapid heartbeat
  • Breathing impairment
  • Fatigue
  • Confusion
  • Seizures
  • High temperature
Benadryl for Dogs: Guide for Dosage, Side Effects and Tips - Side effects of benadryl in dogs

Alternatives to benadryl for dogs

If your dog cannot take Benadryl or want a more natural alternative, you can also use other alternative medicines to treat your dog.

For example, if you are using Benadryl for anxiety in your dog, Anxietrex is a safe remedy that is free of side effects. Remember you should always use it under the vet's prescription.

On the other hand, you can use Derma-lonx for skin irritation and allergic reactions, as it does not have any side effects either. At AnimalWised we'd also like to suggest some homeopathic treatments for dog allergies that can be useful for your pet when combined with medical treatment.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Benadryl for Dogs: Guide for Dosage, Side Effects and Tips, we recommend you visit our Other health problems category.

  • Never give your dog Benadryl without consulting your vet beforehand

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My female dog is in heat. My Male dog will not stop whining. How can I help him?
Bobbie Brenick
Cheyenne Anderson
gonna try baby benedryl for my 5lb chichuahua,he is a long hair and is constantly scratching....praying for relief for him
Administrador AnimalWised
We wish him well!

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