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Benadryl for Dog Allergies

Benadryl for Dog Allergies

Benadryl for dog allergies is an over-the-counter medication more and more dog owners are reaching out for. Many dogs nowadays suffer from debilitating allergies and dog owners seek out information on how to provide their dogs with some relief. Whether your dog was stung from a bug or is having an allergic reaction to some substance, Benadryl for dog allergies may be something you want to keep handy in your dog's first aid kit. Following is some information about Benadryl for dog by veterinarian Dr. Ivana Crnec.

rash on a dog's belly

Signs of Allergies in Dogs 

As weird as it may sound, the whole concept of allergies is relatively new. Before the 20th century, allergic reactions were scarcely known or recognized. In fact, the term "allergy’’ was coined in 1906, by a Viennese pediatrician, Baron Clemens von Pirquet.

However, today, over 10 percent of the population suffers from allergies. As the incidence of allergies has increased in people, there has been a similar increase in allergies in dogs.

An allergy can be defined as a state of over-reactivity or hypersensitivity of the immune system to a particular substance. The substances that hold the power to trigger such reactions of the immune system are called allergens.

Allergens are usually harmless substances that are inhaled or swallowed, or that come into contact with the skin or eyes, thus mistakenly provoking the immune system to produce an antibody called immunoglobulin E (IgE).

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The symptoms of allergies differ, depending on the place where the allergic reaction occurs. In a nutshell, the allergic reaction may occur on: the dog’s skin – associated with either localized or generalized itchiness and skin inflammation or irritation, the lining of the airways – associated with coughing, sneezing, wheezing and discharge from the nose and eyes and the lining of the gastrointestinal tract – associated with vomiting and diarrhea.

Benadryl for Allergies in Dogs

Apoquel for dog allergies

Benadryl is a first-generation ethanolamine-derivative antihistamine with a generic name diphenhydramine. It is a type of antihistamine that can cross the blood-brain barrier. The fact that it crosses the blood-brain barrier increases its efficiency.

Benadryl works by blocking the histamine uptake. Simply put, the active substance in Benadryl blocks the receptors that receive histamines in the body. The body keeps on producing histamines but the blocked receptors cannot register their presence. The situation can be described as when the mailman tries to add new mail to an already full mailbox.

Since it is available over-the-counter, Benadryl is highly popular among dog owners. Its popularity is additionally contributed by the facts that the drug is generally well-tolerated and has wide safety margins.

Benadryl is primarily used for treating environmental allergies and allergic reactions. Diphenhydramine, as the active ingredient in the Benadryl, helps alleviate the common symptoms associated with allergies. Those symptoms include hives, itching, coughing, sneezing, swelling and inflammation, redness, runny nose and runny eyes.

Benadryl is classified as mild to moderately effective antihistamine. Therefore, Benadryl is not potent enough for acute allergic reactions manifested with facial swelling and impaired breathing.

On top of Benadryl being used for allergies, Benadryl can be used to alleviate motion sickness during car and plane rides and to achieve mild sedation. Recently more and more veterinarians are adding Benadryl to the combination of drugs used in the treatment of tumors and heartworm disease.

Simply put, the mast cell degranulation that occurs in patients with tumors is followed by massive histamine release. The histamine release, unless defeated by antihistamines, is likely to trigger allergic reactions. As for the heartworm disease, the drugs used in the treatment often cause allergic reactions which can be prevented by using Benadryl.

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Dose of Benadryl for Dogs 

When dosing Benadryl you should classify your dog in one of the following categories: 30 lbs or less – 10 mg per dose, 30-50 lbs – 25 mg per dose and 50 lbs or over – 50 mg per dose.To be more precise, when used orally, the standard dose is 1 mg per pound of body weight, administered 2 to 3 times a day with at least 8 hours between two administrations.

Exceeding the recommended dosage can have fatal consequences. It should be noted that Benadryl starts taking effect about half an hour after administration. Since the drug can potentially cause nausea and decreased appetite, it is recommended to administer the drug on full stomach.

Most drug-store available tablets are 25 mg which is enough for a 25 pounds dog. Nevertheless, before using the drug, its concentration must be double-checked. Another important factor that needs to be double-checked is the combination of active ingredients. Sometimes, the diphenhydramine is combined with other medications. It is important to make sure the formulation you use contains only diphenhydramine.

It is not recommended to give your dog the full dosage of Benadryl straight away. Instead, give it only a small amount and then wait for a few hours. If the dog does not show any side-effects and symptoms you can safely administer the full dosage.

Liquid Benadryl should be avoided because its high alcohol concentration can be harmful for dogs. The children’s liquid formula is a better alternative since it does not contain alcohol. However, it does contain high concentrations of sodium which can be dangerous for dogs with certain medical conditions. It should also be noted that the dosage for liquid Benadryl is different from the dosage for Benadryl pills.

Time-release capsule forms of Benadryl are also not recommended. This is because dogs have different absorption mechanisms than people and those mechanisms can significantly affect the dosage of absorbed drug. What is more, dogs are likely to chew on the capsule and eventually end up ingesting too much Benadryl in one go.

dog's heart is beating fast

Side Effects of Benadryl for Dogs

As with other drugs, Benadryl for dogs can be unsuitable for dogs with certain conditions and may cause side effects. Benadryl is contraindicated in dogs with angle-closure glaucoma, high blood pressure, cardiovascular conditions, allergic lung disease, bladder neck obstructions, prostatic hypertrophy, seizures, pregnant and nursing dogs and young puppies.

Most side-effects and symptoms occur within the first 1 to 5 hours after Benadryl exposure. Therefore it is highly advisable to have your dog closely monitored during this timeline. The side-effects and symptoms Benadryl may cause are divided in two major groups – common and rare.

The group of common side-effects and symptoms includes dry mouth or hypersalivation, increased breathing rate,
increased heart rate, urinary retention, sedation. The group of rare side-effects and symptoms includes: vomiting, diarrhea, increased or decreased appetite.

As previously mentioned, Benadryl is relatively safe and has wide safety margins. However, allergic reactions and overdosing are a possibility. If the dog’s symptoms worsen upon Benadryl exposure it is safe to assume that the dog is allergic to the drug. Benadryl allergy is more common in certain dog breeds.

On the other hand, if a dog overdoses on Benadryl, its central nervous system becomes hyper-excited, which can potentially be fatal. Signs of overdose include: dilated pupils, seizures, rapid heart rate, agitation and constipation.

In conclusion, all in all, when used adequately and in the right proportions Benadryl is quite beneficial. It is part of a small group of over-the-counter drugs that veterinarians actually recommend.

About the Author

Dr. Ivana Crnec is a graduate of the University Sv. Kliment Ohridski’s Faculty of Veterinary Medicine in Bitola, Republic of Macedonia. She is a certified nutritionist and is certified in HAACP food safety system implementation.

ivana crnec

She currently practices as a veterinarian in Bitola and is completing her postgraduate studies in the Pathology of Domestic Carnivores at the Faculty of Veterinary Medicine in Zagreb, Croatia.

Ivana’s research has been published in international journals, and she regularly attends international veterinary conferences.

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