How long does it take a dog to feel the effects of Benadryl?

Giving Benadryl to your dog: should you do it?

Is it helpful and harmless?

Or is Benadryl for dogs dangerous and a bad idea?

Used properly, in the right situations, Benadryl can be a lifesaver—preventing headaches and alleviating discomfort for your dog.

Before we get started, a disclaimer: it’s always a good idea to talk to your vet about giving medication to your dog. If you can’t make it in for an appointment, try just giving your vet a call to ask their opinion if you’re worried about giving your dog Benadryl.

What Is Benadryl?

Benadryl is a common over-the-counter antihistamine that you can buy at any drug store, pharmacy, or grocery store.

Like other antihistamines, its primary use is to help reduce symptoms associated with allergies such as sneezing and runny nose.

Keep in mind that Benadryl is the brand name for the active ingredient called diphenhydramine. So even if your store doesn’t sell Benadryl, they almost certainly offer a different brand with the same active ingredient. Check the “Drug Facts” on the back of the label and look for diphenhydramine as the Active Ingredient.

Benadryl for Dogs Uses

Benadryl absorbs very quickly and usually begins to take effect after about 30 minutes. Benadryl can be helpful if your dog has any of these symptoms:

• Itchy skin
• Irritated skin
• Nausea
• Car sickness
• Sedatives
• Insomnia
• Anxiety
• Insect or flea bites
• Bee stings
• Reaction to vaccines
• Hay fever, sneezing, or coughing
• Stuffy or runny nose
• Asthma
• Allergies

[bullymax-banner slug=”miracle-vet-vitamins-on-amazon”]

Can I Give My Dog Benadryl? Is Benadryl Safe for Dogs?

Generally speaking, yes.

Benadryl is a relatively harmless drug that should be totally safe for your dog.

But there are a few caveats:

Benadryl might not be safe for puppies. If your dog is a little pup, ask your vet first. Just as you have to be careful giving medications to human babies, you have to be careful with what you give a puppy. They’re small and may not have fully developed

Avoid combination Cold/Sinus medications. Diphenhydramine is safe for dogs—but many of the other cold and sinus ingredients (including fever reducers, decongestants, and expectorants) may not be. Make sure diphenhydramine is the ONLY active ingredient listed on the label.

Steer clear of liquid Benadryl. In liquid form, Benadryl has high alcohol content that will be unsafe for your pet.

It’s counter-indicated with some conditions. If your dog has prostatic disease, glaucoma, cardiovascular disease, or hyperthyroidism, definitely check with your vet to make sure Benadryl is safe for your pet.

Watch for formulas containing sodium. Some Benadryl formulas (such as children’s versions) contain sodium, which could be problematic for dogs with certain health conditions who are taking medications. To be on the safe side, look for a form of Benadryl that does not contain sodium.

Do not exceed the recommended dosage. More details on this below.

Benadryl Dosage for Dogs

How much Benadryl can you give a dog?

The amount of Benadryl your dog needs depends on its size.

The easy (and less precise) way to determine this is to put your dog into one of three categories:

• 30 lbs and smaller – give 10 mg per dose
• 30-50 lbs – give 25 mg per dose
• 50 lbs and over – give 50 mg per dose

That should give you a fairly accurate dosage.

According to the Merck Veterinary Manual, the standard dose for Benadryl is 2-4 milligrams per kilogram of body weight or 0.9-1.8 milligrams (mg) of Benadryl per pound.

Therefore, a simple and practical dose is 1 mg of Benadryl per pound of your dog’s weight, given 2-3 times a day. For example, a 10-pound dog might receive a 10 mg dose in the morning, afternoon, and evening.

Most diphenhydramine (Benadryl) tablets are 25 mg, which would be the appropriate size for a 25-pound dog. Smaller dogs will require you to cut or divide these 25-mg pills. In this case, children’s Benadryl in the chewable tablets may be a good option. These come in dosages of 12.5 mg.

Side Effects of Benadryl

Being a safe medication, Benadryl’s side effects are on the mild side.

The most commonly reported side effect is drowsiness. This is so common that many people give Benadryl to their dogs to help them calm down. (Diphenhydramine is even marketed and used as a sleep-aid by many people.)

The second most common side effect is mild disorientation. We recommend paying attention to your dog’s behavior after giving them Benadryl to make sure they don’t experience this before giving them a second dose.

Other, less common side effects include:

• Dry mouth
• Breathing problems
• Diarrhea
• Lack of appetite
• Vomiting
• Agitation
• Rapid heartbeat
• Urinary retention (not peeing)

If you think your dog is experiencing any of these side effects, give your vet a call.

Tips for Giving Benadryl to Your Dog

Test it first. Instead of giving your dog a full dose right off the bat, try giving them a small amount of Benadryl and waiting for a few hours. Watch your dog for any signs of side effects or reactions.

Always give it with food. One way to avoid some of Benadryl’s side effects (such as nausea and lack of appetite) is to give it to your dog with a meal or a dog treat.  Bully Max High-Performance, high calorie dog food is good for this.  

Break up tablets and put it into a piece of meat. Most dogs are less than eager to swallow a whole pill. But if you break the pill up into chunks and place them inside a piece of meat, your dog will wolf it down without ever knowing there was a pill inside.

Mix liquid gel Benadryl with wet food. If you have a liquid gelcap, try breaking it open and mixing it with some wet food containing gravy. Your dog will never taste the Benadryl (and they’ll love the gravy).

[bullymax-banner slug=”miracle-vet-vitamins-on-amazon”]

Diphenhydramine (brand name: Benadryl®, Vetadryl®, Banophen®, Genahist®, Diphenhist®, Unisom®, Sominex ®) is an antihistamine used in cats, dogs, ferrets and other small mammals, birds, horses, and cattle to treat allergic reactions, motion sickness, and vomiting. It is also used as a mild sedative, and is one of the therapies for mast cell tumors.

Its use in small and large animals to treat allergic reactions and other conditions is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their direction may be significantly different from those on the label.

How is diphenhydramine given?

Diphenhydramine is given by mouth in the form of a tablet, capsule, oral liquid, or liquid injection. The oral formulations can be given with or without food. If your pet vomits after dosing on an empty stomach, give future doses with food or a treat. The liquid has a bad taste to cats, and administration by mouth may be difficult. The injection is typically given in the hospital, either in the vein, muscle, or under the skin.

This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

The most common side effect is lethargy, dry mouth, and urinary retention. Vomiting, diarrhea, and lack of appetite are also possible. Excitement rather than lethargy can occur occasionally, especially in cats. Diphenhydramine can alter the results of skin allergy testing; discontinue this medication at least 2 weeks before testing.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Diphenhydramine should not be used in patients that are allergic to it or similar antihistamines. Do not use in pediatric or neonatal pets. Diphenhydramine should be used cautiously in pets with glaucoma, prostate enlargement, intestinal or bladder obstruction, COPD, elevated thyroid hormone, heart disease, or high blood pressure. Use with caution in pets that are pregnant or lactating, geriatric, or are working dogs.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with diphenhydramine: anticholinergic drugs, tricyclic antidepressants, and CNS depressant agents such as sedatives, anesthetics, and pain medications.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet at home for adverse effects.

How do I store diphenhydramine?

All formulations of diphenhydramine should be stored at room temperature between 15°C and 30°C (59°F to 86°F) and protected from light. Oral liquids should be protected from freezing.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.