Benadryl For Dogs: Dosage, Side Effects, And Alternatives – Relievet

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Benadryl For Dogs: Dosage, Side Effects, And Alternatives

Author: Nali Macklin - April 24th 2020

 Accuracy Review & Edit: Nicole Wanner, DVM - May 20th 2021

dosage of Benadryl for dogs side effects and alternatives

Most of us will find Benadryl in our medicine cabinet. It is a widely available drug used to treat symptoms of conditions such as seasonal allergies, motion sickness, and hay fever in humans. 

So, if it works for us, what about Benadryl for dogs?  

Ask around, and you will find that many dog owners have also given their dogs Benadryl to treat various conditions such as allergy symptoms, motion sickness, and even anxiety. In some cases people also give Benadryl to cats.

This popular drug is one of the few over-the-counter medications that the vet often recommends for owners to administer at home to their dogs and cats.

Table Of Contents

What is Benadryl used for in dogs?
Types of Benadryl for dogs
How does Benadryl work?
Is Benadryl safe for dogs?
Dosage of Benadryl
How long does it take for Benadryl to work in dogs?
Side effects of Benadryl
How does Benadryl interact with other drugs?
Natural alternatives to Benadryl

What is benadryl used for in dogs?

  • Allergies:  Benadryl is a brand name for a type of drug known as Diphenhydramine – an antihistamine used to relieve symptoms of allergies, such as rashes, itching, and dog eye allergies that can come from seasonal or environmental allergens.  
  • Anxiety: Benadryl contains soothing properties, which can promote calmness in dogs during high-stress situations (i.e., fireworks, thunderstorms). 
  • Insomnia: For dogs with trouble sleeping, Benadryl can make your dog feel drowsy and promote sleep.   
  • Itching: Diphenhydramine can decrease itching and minimize the reaction of insect bites and bee stings.   
  • Motion sickness: Since the active ingredient in Diphenhydramine is similar to the active ingredient found in Dramamine (a motion sickness drug), Benadryl can be useful to treat nausea and motion sickness when traveling. 

While Benadryl is FDA approved for human use, it is not FDA approved for animal use, though some types of Benadryl are considered relatively safe for dogs and cats.   

Types of Benadryl for dogs

  • Liquid: Benadryl is available in liquid form, but it is toxic for dogs because it contains alcohol. Therefore, you should not give it to your dog.
  • Tablet: Each Benadryl tablet contains 25 mg of Diphenhydramine. Your dog will likely hate swallowing the pill, so you might need to hide it in a delicious treat each time. Never use the time-release tablets as they are hard to dose correctly in dogs; the reason for this is that tablets are absorbed differently in dogs than in humans.
  • Children's liquid formula: If you prefer to use a liquid Benadryl, the children's formula contains no alcohol. It is also less concentrated and has a lower dosage range, which might be more suitable for owners of small dogs since it will be easier to measure out.
  • Spray: Benadryl spray can be used in emergency cases where your dog can't breathe due to swelling from insect bites and allergic rashes. However, spraying Bendaryl on open or raw wounds can sting, causing significant discomfort to your dog.
  • Topical: Benadryl also comes in gel or cream form that you can apply directly to your dog's itchy skin. Keep in mind though that irritation can occur after prolonged use. If the skin becomes infected your vet may recommend an antibiotic like Cephalexin for dogs
  • Injection: For severe allergic reactions, your veterinarian can administer an injection of Benadryl. The treatment can be given in the muscle, vein, or under the skin.

How does Benadryl work?

An allergic reaction causes a chemical release of histamine in the body. Once released, histamine binds to receptors on specific cells, causing itchiness and inflammation. These receptors are known as H-1 receptors.

Benadryl (or Diphenhydramine) is an antihistamine and works by blocking the H-1 receptors and decreasing the effects of histamine.

When you give your dog Benadryl for motion sickness, it works by blocking the impulses to the vomiting center in the brain of the dog.  

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Is Benadryl safe for dogs? 

It is possible for dogs to overdose on Benadryl, and the symptoms can be life-threatening. If you notice any of these symptoms, contact your vet or emergency veterinary hospital immediately.

  • Abnormal heart rate
  • Aggression or agitation
  • Constipation
  • Dog Breathing Problems
  • Dilated pupils
  • Extreme drowsiness
  • Muscle tremors
  • Red eyes
  • Seizures

Ironically, Benadryl can cause an allergic reaction in some dogs. Just as with all drugs, you should always watch your dog closely after their first use.  

Dosage of Benadryl

As an approximate guideline, the maximum dosage of Benadryl for dogs is 1mg for every 1 pound of the dog's body weight, given 2-3 times per day, about 8-12 hours apart.

Many factors can change this general guideline, so you should always talk to your vet to determine the proper dosage for your dog.

In general, start with a lower dose and gradually increase it until the desired effect is reached. Some dogs are more sensitive to Benadryl than others, so starting small is best.   

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  • Liquid: As mentioned earlier, Benadryl in liquid form is toxic to dogs because it contains alcohol; therefore, you should not give it to your dog. Instead, the Children's liquid formula is a safer choice. See the chart below.
  • Tablet: Each Benadryl tablet contains 25 mg of Diphenhydramine (1 tablet for a 25 lbs. dog), but always check the dosage on the package and never assume that every product will have the same dosage. See the chart below.

    Make sure that the Benadryl you're giving your dog contains only Diphenhydramine and is not combined with other drugs such as Tylenol as it can cause harmful side effects. 
  • Topical: When applying the topical to your dog's skin, test a small area first to make sure there are no allergic reactions. Never apply gel or cream to your dog's skin if it's blistering. Overdose can happen if you are also giving your dog Benadryl tablets to treat the symptoms.
  • Injection: The injectable Benadryl is available in 10 mg/ml and 50 mg/ml. Your vet will determine the correct dosage to administer based on the symptoms. 
Max Dose (every 8-12 hours)Max Dose (every 8-12 hours)
Dog WeightTablet (mg)Children's Liquid (ml)
1 lbs – 10 lbs1 mg – 10 mg0.4 ml – 4 ml
10 lbs – 20 lbs10 mg – 20 mg4 ml – 8 ml
20 lbs – 30 lbs20 mg – 30 mg8 ml – 12 ml
30 lbs – 40 lbs30 mg – 40 mg12 ml – 16 ml
40 lbs – 50 lbs40 mg – 50 mg16 ml – 20 ml
50 lbs – 60 lbs50 mg – 60 mg20 ml – 24 ml
60 lbs – 70 lbs60 mg – 70 mg24 ml – 28 ml
70 lbs – 80 lbs70 mg – 80 mg28 ml – 32 ml
80 lbs – 90 lbs80 mg – 90 mg32 ml – 36 ml
90 lb – 100 lbs90 mg – 100 mg32 ml – 36 ml
100 lbs – 110 lbs100 mg – 110 mg40 ml – 44 ml
110 lbs – 120 lbs110 mg – 120 mg44 ml – 48 ml
120 lbs – 130 lbs120 mg – 130 mg48 ml – 52 ml
130 lbs – 140 lbs130 mg – 140 mg52 ml – 56 ml
140 lbs – 150 lbs140 mg – 150 mg56 ml – 60 ml

How long does it take for Benadryl to work in dogs?

It usually takes 24 hours for Benadryl to wear off and stop working. However, for dogs with liver or kidney disease, the effects can last longer. Always talk to your veterinarian before giving Benadryl, especially if your dog has chronic liver, kidney, or heart problems.

Side effects of Benadryl

Benadryl side effects in dogs are similar to those in humans. Common side effects include dry mouth, sleepiness, and urine retention.

Some dogs may experience rare side effects, such as diarrhea, vomiting, rapid breathing, increased heart rate, and appetize changes. If these symptoms become severe, you should call your vet.

Dogs with the following conditions should not take Benadryl without first consulting with the vet:

  • Allergic lung disease
  • Bladder neck obstruction
  • Cardiac conditions (such as cardiovascular disease, heart failure)
  • Pregnant or nursing
  • Glaucoma
  • High blood pressure
  • Hypertension
  • Hyperthyroidism
  • Low blood pressure
  • Prostatic hypertrophy
  • Seizure disorders

How does Benadryl interact with other drugs?

Benadryl can reduce the effectiveness of prokinetic drugs (metoclopramide, cisapride) used for constipation and other GI problems.

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Natural Alternatives to Benadryl

If you aren't comfortable giving Benadryl to your dog, or you are just looking for a safer natural alternative, you might want to consider CBD.

CBD works with your dog's endocannabinoid system to keep their bodily systems in balance, including those which regulate the symptoms of allergies.

The following research has shown that CBD may positively impact symptoms of inflammation and allergy. Research is still in its early stages, though, and no studies of CBD for allergies have been done in dogs yet. Never use CBD to replace an existing prescription medication without consulting your vet.

A rodent study back in 2013 found that CBD helped relieve symptoms of lower airway obstruction, a symptom of asthma.

Inflammation is another significant contributor to allergies in dogs. A 2011 study found that CBD reduced inflammatory markers in the gut in mice.

While this early research is promising, its important to note that these are relatively small and limited studies, so we cant draw a full conclusion from them. 

We make natural CBD chews and CBD oil for dogs of all sizes, with concentrations ranging from 150mg up to 1500mg/CBD per 30ml to ensure that even the largest dogs will receive an effective dose.

The legal hemp-derived CBD in our products is organically grown in Colorado and then carefully refined at a low temperature. We use this method to make our products safe and effective for dogs by removing 100% of the THC while keeping many of the naturally occurring terpenes, flavonoids, and minor cannabinoids intact.

We combine the extract with coconut-derived MCT oil, a well-known beneficial supplement for dogs and humans. The finished product is then 3rd party lab-tested to ensure it is free of anything harmful.


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