Benadryl for Itchy Dogs: FAQ with Our Vet

Many owners will have tried antihistamines in an attempt to treat their itchy dog from home, before coming in to my vet clinic. Benadryl is readily available and inexpensive, making it an attractive choice. It is also generally seen as quite safe; amongst both people and animals.

Frustratingly, from my experience, antihistamines like Benadryl are not very effective. This is especially true when the dog has more than just mild itching and when they have secondary skin infections. Something like Benadryl is not something I tend to prescribe for itchy dogs, as I have access to other medicines which work much better (including steroids and Apoquel).

Is Benadryl effective in treating itchy dogs?

When compared to other medicine available to us, Benadryl is not very effective at relieving itchiness in out canine companions, no.

According to one published study ‘Type 1 receptor antihistamines are notorious in their inconsistency in reducing pruritus in atopic dogs (1).’  Inconsistency is a key word here; results are simply not seen in all dogs and, for many, antihistamines like Benadryl have no effect.

This study, however, did demonstrate decreased itch in 60% of participants (2). The most effective antihistamine was not found to be Benadryl, but one called Hydroxyzine.

While 60% may seem like a good result, it is unlikely the dogs experience such rapid or effective relief as is achieved by other anti-itch medication which we have available to us. Also, keep in mind, a whopping 40% did not see any improvement at all in their signs.

Is Benadryl Safe for dogs?

One of the best things about Benadryl is how safe and well tolerated it is. For most dogs, side effects are rare.

Still, it is important to consult with your vet before using it and to double check that you are giving it at the correct dose.

How much Benadryl can I give my dog for itchiness?

The dose is from 2mg to 4mg per kilo every 8-12 hours. For a 10kg dog, this means from 20 to 40mg two or three times a day.

It is advised to give it over the course of a few days, to see if it is having any effect. A one off dose may not be enough to notice improvements.

Is there anything else I need to keep an eye on if my dog is itchy?

Absolutely, yes. Itchiness in dogs is not always a straightforward or easy issue to treat and there can be many causes.

We want to ensure our itchy dogs are up to date with their flea and mite prevention. We also want to check their skin for any signs of redness, scabs or fur loss. This is an indication of a more serious issue, which would require vet attention.

If your dog is experiencing sudden onset or intense itching, be aware that this could be a sign of an allergic reaction. Other symptoms to watch for would include swelling (of e.g. the neck, face or paw), hives, pale gums or wheezy breathing.

What are other over-the-counter itch relief options?

There are a range of anti-histamines available OTC for dogs including Benadryl (Diphenhydramine), Piriton (Chlorphenamine) and Zyrtec (Cetirizine). Some may work to reduce itching in a proportion of dogs.

A medicated wash like Hibiscrub is also available to buy OTC and can be effective at reducing the level of yeast and bacteria on the surface of the skin, reducing itching.

For the majority of dogs though, prescription products will be much more effective than anything that can be bought over the counter.

What else can I do at home to help an itchy dog?

It is wise to try and determine what is making your dog itchy. This can mean keeping an ‘itchy diary’ and grading their itchiness from a 0 to a 10, keeping note of where they went that day, what they had to eat, what the pollen count was and what the weather was like.

When it comes to allergies in atopic dogs, finding out what the dog is allergic to and then avoiding it is really key.

In case of parasites, always make sure an itchy dogs is up to date with an effective flea and mite prevention.

What are the most frequent reasons dogs are very itchy?

• Flea Allergy Dermatitis: In the summer, I see a huge number of dogs affected by flea allergy dermatitis. We can remedy this issue by ensuring dogs are routinely treated for fleas, and that any other cats, dogs and rabbits in the home are treated too. The house should be deep cleaned and a flea spray used, to eliminate the flea burden within the home. For those who are very itchy or who have broken skin, a vet visit is advised and they may well benefit from some strong anti itch medicine (like steroids) and antibiotics.
• Environmental allergies: An estimated 1 in 7 dogs have environmental allergies and they can present at any time before the age of five. Avoiding the trigger is key. This can mean e.g. walking your grass allergic dog on pavement and wiping off their paws and belly with doggy wet wipes when they come inside. These dogs benefit from regular bathing as well as skin supplements, to help strengthen their skin barrier and make it more robust, preventing the entrance of allergens.
• Food allergies: To determine what your dog is allergic to, you could trial an elimination diet or hydrolyzed diet, for a period of 6-8 weeks. During this time, be sure your dog is not also snacking on things like human scraps, dental sticks or treats! For many dogs with allergies, their skin will be so inflamed and irritated, they will need prescription medicine to control flare ups, and allow their skin to settle back down. This can include anti-itch medicine like Cytopoint injections and Apoquel tablets, as well as medicated washes and course of antibiotics.
• Contact dermatitis: Dogs can develop red, sore and itchy skin after coming in contact with an irritant such as a cleaning product or nettles. We should bathe the affected skin with warm, soapy water ASAP and provide the dog with an antihistamine such as Benadryl or Piriton after confirming with their vet if this is a suitable option. If signs persist or are worsening, a vet visit would be needed. Some dogs will be issued with prescription medicine such as topical steroids, to reduce the local inflammation.

When do I need to consult with my vet if my dog is itchy?

Most itchy dogs benefit from the input of their vet. Too often, I see dogs who have come into the clinic for the first time after struggling with itchy skin for weeks or even months from home. Owners have tried a huge laundry list of OTC products that have not worked and are desperate to help their dog.

With the use of the right prescription medicine, we can usually get these dogs itch free in a matter of days. Delaying treatment can lead to chronically inflamed skin, deep skin infections and a reduced quality of life, so is never recommended.

Only the very mildest itch is something we should try and treat from home. If the treatment we use is not effective within a day or two, the skin is broken or the dog seems uncomfortable, a vet visit is best.

FAQ

How fast does Benadryl work?

Benadryl usually gets to work within 30-60 minutes or so.

Will Benadryl make a dog sleepy?

Some patients experience drowsiness,  and whether or not this happens will be affected by age, breed and any underlying medical issues the dog has. Side effects such as drowsiness should last no more than 12 hours.

Which antihistamine is best for skin itching?

I personally do not find any antihistamine especially effective for itchy skin, especially when the dog has been itchy for some time and/or has underlying skin infections. In general, prescription medicine is much preferred.

The antihistamine I use most often would be Piriton as I find it causes least side effects.

1. https://link.springer.com/chapter/10.1007/978-3-662-44605-8_19
2. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1748-5827.1994.tb03867.x