Is Benadryl Good for Dogs?


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No one ever wants to see their dog suffer, but often pet owners are far too ready to reach for a “human” medication to treat their pet’s discomfort. Sometimes, the results can be disastrous, because many medications that are good for people are actually toxic to dogs. Over-the-counter pain relievers, for instance, can contain ingredients that can cause severe illness, organ failure, and even death.

What about Benadryl, though? Is Benadryl good for dogs?

Allergic Reactions

Dogs are very much like humans in that they can develop itching or allergic reactions to any number of substances. Common culprits could be food ingredients, pollen, parasites (fleas, for instance), mold or mildew. The results can range from sneezing to itching or hives, and even diarrhea. The intensity of the reaction will depend on how sensitive your dog is to the particular allergen.

If the reaction is on the low end of the scale (a bit of scratching, somewhat loose stools or sporadic sneezing), I’d hesitate to turn to medication as the first course of action. On the other hand, if your dog is clearly uncomfortable due to an allergic reaction, you should take measures to ease his discomfort.

So, is Benadryl good for dogs? Yes. In fact, it’s one of the very few human drugs that is very well tolerated by dogs, and the likelihood of harmful side effects is slim to none. There are a few things that you should consider, though, before you head down to the pharmacy and grab a bottle of Benadryl for your dog.

The Basics

Benadryl is actually a brand name for diphenhydramine, which is an antihistamine. You might also find diphenhydramine sold under a store brand, or “generic” label. The store brands are cheaper than the brand name, but it’s wise to check the ingredient list carefully. It’s known that Benadryl is good for dogs, so if you’re looking at a generic brand, make sure that the ingredients are identical to Benadryl.

Diphenhydramine works by stopping your brain from sending the signals that create allergy symptoms. In other words, when you take Benadryl, it causes your brain to tell your body to stop itching, your nose to stop running, and so on. Is Benadryl as good for dogs in this regard?

Indeed it is. Benadryl works essentially the same way on the canine brain as it does on the human brain.

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Side Effects

I’ve said that there is little to no chance of harmful side effects if you give your dog Benadryl. That doesn’t mean that there are no side effects at all, though.

If you’ve ever taken Benadryl, or other diphenhydramine products, then you know that the most common side effect is drowsiness. In fact, this is why diphenhydramine is also sold as an over-the-counter sleep aid, under brand names like Nytol and Sominex; it’s because antihistamines make people sleepy.

This can actually be an advantage where your dog is concerned. If he’s sleepy, he’ll get the rest he needs in order to fight the allergic reaction. If the allergy has manifested as a skin irritation, too, your dog is going to be scratching far less if he’s sleeping more.

Benadryl Good for Dogs

One way, though, in which Benadryl affects a dog’s brain differently than it does a human’s brain is that in dogs, Benadryl suppresses vomiting. This makes it useful if you are trying to prevent a reaction to something that you know your dog is allergic to, but that’s unavoidable. One such example might be pollen; it’s likely not realistic to think that your dog is going to be indoors all the time during the spring and summer, and never encounter pollen. So, you might use Benadryl as a preventative medication for your dog, the same way as you would for a human.

Usually, you won’t have to worry that doing so would be rendered useless if the dog should vomit up the medication. However, Benadryl only suppresses the urge to vomit; it’s not going to eliminate it entirely. This is actually a good thing, though, because if your dog should ingest something harmful, vomiting is usually going to be his way of getting rid of the harmful substance.

Is Benadryl Ever Not Good for Dogs?

If your dog’s only health issues are allergies or occasional itching, then you can safely administer Benadryl with a clear conscience; your vet won’t even give you a hard time if you don’t clear it with him or her. However, if your dog has other medical issues, caution is warranted. Sometimes, Benadryl can hamper the effectiveness of other drugs that your dog might be taking. So, if your best buddy is on any other type of medication, you definitely have to ask your vet before adding Benadryl into the mix.

Benadryl can also have an adverse effect on certain medical conditions. If your dog has cardiovascular disease, glaucoma, lung disease or (in males) an enlarged prostate, again, check with your vet before administering Benadryl. In fact, any time that you even suspect that giving Benadryl to your dog might be harmful, check with your vet. It’s better to do nothing at all than to inadvertently harm your dog.

How Much Benadryl Is Good for Dogs?

The proper dose of Benadryl depends on your dog’s bodyweight. The math on this is pretty easy, though: the basic rule of thumb is to give your dog a milligram of Benadryl for each pound of his bodyweight. You can repeat the dose every 8-12 hours.

If your dog weighs 25, 50, 75 or 100 pounds, or another multiple of 25, it’s really easy to get an accurate dose, because Benadryl tablets are available in 25 and 50 milligram sizes. If your dog’s weight is not a multiple of 25, you might want to go with liquid Benadryl, which is easily mixed into wet food, or administered orally by using a syringe (minus the needle, or course!). Just make sure to double-check the dosage.

Also, I’ve mentioned before that you should check the ingredient list. If you’re buying Benadryl or a Benadryl clone, you’re fine. But keep in mind that diphenhydramine is sometimes combined with other drugs (Tylenol, for instance). You want to be sure that you’re offering only diphenhydramine. Anything else could prove toxic.

Knowing When to Call the Vet

The question “Is Benadryl good for dogs?” is really only appropriate in the context of minor to moderate canine allergic reactions. If the reaction is severe or acute (for instance, if the dog is having trouble breathing, or if his face is swelling), then please don’t waste time trying to treat the condition with Benadryl. Take your dog to the vet, and do it right away. If it’s outside your regular vet’s hours, go to an emergency clinic.

With a serious allergic reaction, you should never wait to seek treatment. Don’t assume that your dog can wait until the clinic opens; you could be risking his life if you wait.

In an emergency, your vet can prescribe something considerably more heavy-duty than Benadryl, and can also have your dog tested to determine what caused the allergic reaction. Once the cause is identified, treatments can be recommended, and medications prescribed to control future outbreaks.

Related Content:

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The Final Word

Is Benadryl good for dogs? In most cases, it offers the same benefits to dogs as it does to humans, and without harmful side effects. If your dog has mild or moderate allergies, a dose of one milligram of Benadryl for each pound of his bodyweight can make him far more comfortable and will usually clear up the problem quickly. More serious allergic reactions, though, will require veterinary intervention.