Benadryl for Dogs: Everything You Need to Know

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Whether you’re the proud owner of a brand-new puppy or your senior pooch has been a member of your family for years, no pet parent ever wants to see their beloved companion suffering from any sort of health condition, big or small. There are times you may be tempted to treat your dog with home remedies, or even consider using medications intended for people.

However, what may be perfectly safe for a human may not apply to your dog, even if it seems like a relatively harmless drug. That’s why it is always recommended to look for natural alternatives like CBD for dogs or proceed with caution when administering medications to your family pet and check with your vet’s office first before giving your dog any kind of medication. This article will talk about Benadryl and its side effects for dogs, as well as the various instances your veterinarian may prescribe this well-known allergy treatment to your four-legged friend.

Understanding The Medication: What Is Benadryl?

Benadryl is actually a brand name for several different antihistamine medications, created for humans and used to treat allergies. In the US and Canada, it refers to the active ingredient diphenhydramine HCL. Diphenhydramine works by blocking receptors on certain muscles and blood vessels that receive histamines, relieving food allergy or environmental allergy symptoms such as excessive sneezing, itching, and hives. Since Benadryl is capable of crossing the blood-brain barrier, which can also render it harmful if misused. Diphenhydramine has not been FDA approved as safe for dogs, therefore it is imperative to consult with your veterinarian before giving it to your pet.

How Can Benadryl Tablets Help My Dog?

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Benadryl is a common over-the-counter (OTC) antihistamine medication used by humans to treat allergy attacks, hay fever, and other allergic reactions. It is frequently prescribed by vets as a treatment for itchiness in dogs due to canine skin allergies, as well as reducing the symptoms that typically accompany allergic reactions.

In the event that your veterinarian deems it a safe therapy for your dog, Benadryl is often prescribed to treat mild to moderate canine allergies (such as seasonal hay fever), since it inhibits histamine release and mucus production. Your vet may also use it to treat more specific allergic reactions such as:

  • Anaphylaxis
  • Bee Stings
  • Environmental Allergies
  • Flea or other Insect Bites
  • Food Allergies
  • Hay Fever, Sneezing or Coughing
  • Hives
  • Itchy Skin
  • Nausea
  • Red/Irritated Skin
  • Runny Nose & Eyes
  • Snake Bites
  • Stuffy or Runny Nose
  • Swelling & Inflammation

Benadryl can also be a useful treatment if your dog suffers from any of the following symptoms other medical/physical conditions:

  • Anxiety
  • Asthma
  • Car Sickness
  • Insomnia
  • Motion sickness
  • Reactions to Vaccines

Because one of the common side effect of Benadryl in dogs is drowsiness, your vet may use it to alleviate dog anxiety, particularly associated with traveling and motion sickness that may occur during plane rides or car trips. However, if you are looking for a more natural option, using CBD for pets might help with anxiety during long plane rides and road trips.

Did You Know…

Veterinarians have been known to prescribe oral Benadryl for other health conditions besides dog allergies and motion sickness – in fact, it has been used to treat dogs with mast cell tumors. The medication helps to mitigate the effects of the exorbitant histamine release caused by mast-cell degranulation. Benadryl has also been used as an adjunct therapy for other medical conditions, including heartworm treatment therapy.

Is Benadryl Safe For Dogs?

As is the case of administering any medication, it is highly recommended to make a veterinary consultation before giving any drug to your dog. During your dog’s check-up, be sure to ask questions about his condition if he appears to be suffering from an allergy attack, and have his complete medical history available, including any medications he may be taking. Once your vet has conducted a complete physical, he or she will be able to determine the cause of the dog allergies, or if his symptoms are indicative of another underlying health condition.

Giving your dog Benadryl without a definitive diagnosis can be not only ineffective, but dangerous. For example, your dog’s red, watery eyes may look like an allergic reaction, but he could be suffering from glaucoma, in which case Benadryl is not only useless, but can actually worsen your pooch’s condition. Keeping this in mind, the benefits of scheduling an appointment with your trusted vet’s office are two-fold: providing an accurate determination of your dog’s condition, as well as the safest form of therapy – a win-win for you and your pet!

What Are The Side Effects Of Benadryl For Dogs?

As a dog owner, it’s essential to be aware of the Benadryl for dogs side effects in the instance that your dog’s veterinarian prescribes it. In addition to informing your vet of any medications your dog is currently taking to avoid potential drug interactions, it is wise to ask if it can worsen a preexisting medical condition.

Some common side effects that occur in dogs who have been treated with Benadryl include:

  • Decrease in Urination
  • Dry Mouth
  • Hypersalivation
  • Increased Heart Rate
  • Loss of Appetite
  • Rapid Breathing/Difficulty Breathing
  • Sedation
  • Urinary Retention
  • Vomiting

In some rare cases, your dog may also experience diarrhea, vomiting, and an increase or decrease in appetite. You may also notice that Benadryl does, in fact, make your dog sleepy. The majority of side effects occur within the first hour of administration, so monitor your dog’s reaction carefully during this time frame. In the event that his reactions are severe, contact your dog’s veterinarian immediately.

Important: If your pooch has any of the following health conditions, use the dog Benadryl only after you’ve consulted your vet:

  • Allergic Lung Disease
  • Angle Closure Glaucoma
  • Bladder Neck Obstruction/Bladder Disorders
  • Cardiovascular Disease
  • Enlarged Prostate
  • High Blood Pressure
  • Hyperthyroidism
  • Known Sensitivity To Diphenhydramine
  • Pregnancy
  • Prostatic Hypertrophy
  • Seizure Disorders
  • Vomiting (due to obstruction at the pylorus)

In addition, please note that Benadryl may react with the following drugs:

  • Amitraz
  • Central Nervous System Depressants
  • Epinephrine
  • Furazolidon
  • Heparin Sodium or Calcium
  • Selegiline
  • Warfarin Sodium

Benadryl Dosage for Dogs: Always Ask Your Vet

benadryl for dogs side effects_canna-pet

Even though generic dog’s Benadryl is a common OTC medication that is used frequently by humans, our four-legged friends require specific dosages that are dependent on many factors, including their body weight, existing medical conditions, and any underlying health issues they may have. It should also be noted that the effects of the dogs Benadryl can be detrimental to pregnant or nursing dogs, and is not recommended under these circumstances. Similarly, it may not be safe for puppies, so consult your vet before administration.

In the event that your vet does approve Benadryl as a suitable treatment for your dog’s allergies, motion sickness, anxiety or other form of therapy, it is vital to follow your vet’s exact dosage instructions, including what time to give your dog his medication and any changes that need to be made in his daily routine. Be sure to ask any other questions you may have about administering his medication, as it is better to err on the side of caution when it comes to your dog’s safety.

Did You Know…

If you’ve missed a dose of Benadryl, your vet will most likely suggest that you give your dog the missed dosage as soon as possible. Avoid giving your pet two doses at once. If you have specific questions regarding dosage information/missed dosages, be sure to contact your vet immediately to avoid complications, improper administration or an overdose.

Benadryl & The Risk Of Overdose In Dogs

To ensure you don’t run the risk of overdosing your pet, the following information outlines the signs and symptoms of Benadryl overdose in dogs:

  • Hyper-excitability of the central nervous system (CSN)
  • Agitation
  • Constipation
  • Difficulty Breathing
  • Dilated Pupils
  • Extreme Fatigue
  • Fast or Irregular Heartbeat
  • High Temperature
  • Seizures
  • Tremoring Muscles / Muscle Spasms

If your dog displays any of the aforementioned symptoms or you believe your dog may have experienced an overdose of Benadryl, contact your vet’s office or emergency veterinary hospital right away.

In some instances, your dog may develop an allergic reaction to Benadryl – if you notice signs of an allergic reaction, immediate veterinary care is required. If it’s the first time your dog has been prescribed Benadryl by your vet, be sure to observe him carefully for any worsening symptoms or new conditions.

Is Benadryl A Safe Treatment For My Dog?

Although Benadryl has been utilized by veterinarians in many instances as an effective treatment for dogs who experience allergic reactions, motion sickness and anxiety, it must always be approved by your vet before administering to your pet. If it’s the first time you are giving your pooch a dosage, be sure to watch him closely to ensure he isn’t experiencing any adverse reaction.

In the event that you have questions about proper dosage, medication side-effects, storage information or other related issues, call your vet’s office for additional information and advice.

Giving Your Dog Benadryl: Tips For Administration

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As a disclaimer, the following tips only apply if you’ve received the express consent of your veterinarian to administer Benadryl to your dog. It is essential to follow your vet’s instructions when giving your dog his dosages; be certain to ask questions regarding your dog’s diet and other daily rituals to ensure safe drug administration:

  • Test It Out: If it’s the first time you’re giving your dog Benadryl, you may wish to try giving him a small amount and wait a few hours to see how he reacts. If you notice any adverse reactions or side-effects, call your vet to see how you should proceed.
  • Give It With Food: If your vet approves it, you may want to consider administering your dog’s Benadryl with his meal or a treat, as it may counteract some of the common side-effects, including lack of appetite and nausea.
  • Break Up Tablets Into Food: In most cases, it’s not easy getting our dogs to swallow a pill. In the event your dog has been prescribed Benadryl in tablet form, you may wish to break up his individual dosage into chunks and place it inside a piece of meat or mix it into his bowl – this works especially well with dogs who are averse to taking their medication.
  • Mixing Liquid Benadryl With Wet Food: Although Benadryl for dogs is usually administered in tablet form, your vet may prescribe it in a liquid form if he/she deems it safe. In this case, mix it into your dog’s wet food for easy dosage during meal-time.

Did You Know…

As mentioned earlier, Benadryl comes in many forms – there is a very wide range of Benadryl products available at drug stores and pharmacies intended for human usage; most forms of this common antihistamine also contain the active ingredient Cetirizine (another form of antihistamine), while others also contain Pseudoephedrine and Acetaminophen (also listed as Paracetamol or APAP).

These last two ingredients are very dangerous for dogs, so be sure to ask your veterinarian which form you should be giving your dog if he or she has approved it for therapy. Always read the labels carefully and call your vet’s office with any questions if you are uncertain about ingredients, dosage or other pertinent details. In addition, be sure to only administer the type of product advised by your veterinarian – for example, although time-released capsules are commonly used by humans, they can pose serious health risks to your dog.


  1. “Benadryl for Dogs and Cats.” PetMD, 15 Nov. 2017.
  2. Clark, Mike. “Benadryl For Dogs: Dosage, Uses, And Side Effects.” Dogtime, 21 June 2018, Accessed 15 Nov. 2017.
  3. “Benadryl Poisoning in Dogs – Symptoms, Causes, Diagnosis, Treatment, Recovery, Management, Cost”. Wag!, 30 Sept. 2016, Accessed 15 Nov. 2017.
  4. Pena, Melvin, and Stephanie Osmanski. “Is Benadryl Safe for Dogs?” Dogster, 26 July 2018, Accessed 15 Nov. 2017.
  5. “5 Things Dog Owners Should Know About Giving Benadryl To Dogs.”, 21 Aug. 2017, Accessed 15 Nov. 2017.

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