The general rule of thumb is that human medicines aren’t safe for dogs. For instance, giving your pooch paracetamol can cause liver failure.
However, you might have read somewhere that dogs can have antihistamines in a pinch if they’ve been stung by a bee, or your vet might have told you to try giving your dog Benadryl if they’ve been suffering from allergies. So can dogs have antihistamines?
Some types of antihistamines are safe to use in healthy, adult dogs and they can be an effective part of a treatment plan to combat canine allergies.
However, dogs don’t respond to all kinds of antihistamines. Some will work, while others don’t seem to do anything. This varied reaction seems to depend on the individual dog, which means you might have to try several different kinds of antihistamines to find one that works for your pooch. In addition, antihistamines just don’t offer a complete fix for your pooch’s allergies on their own.
If your dog is prescribed antihistamines you will need to try them for 2-3 weeks to see if it helps. If it doesn’t, you’ll need to stop giving it to your dog and try another until you find one that works, following the advice of your vet.
There are also a number of potential side effects your dog might have after taking antihistamines, including drowsiness, an tummy upset, hyperactivity, drooling and an increased heart rate.
This is in general though, and antihistamines aren’t safe for every dog to take depending on their specific needs or underlying health conditions. You must always check with your vet if antihistamines are safe for your individual dog before you give them any.
There are some antihistamines formulated for use in pets and these are generally safe to use as long as you follow the recommended dosage from your vet. However, your vet might prescribe human antihistamines that you can get over the counter at pharmacies. So are these still safe for your dog?
Antihistamines with the active ingredients of diphenhydramine, chlorpheniramine, cetirizine, clemastine or loratadine are usually safe for most healthy adult dogs. Hydroxyzine is another dog-safe antihistamine and one of the most effective available, but it’s only available on prescription.
The antihistamines we humans buy from the chemist are usually sold under a brand name, so you must check the label to see what the active ingredient is and make sure it’s one that’s safe for dogs.
As well as checking what the active ingredient is, you need to check that the medicine doesn’t contain other ingredients. If your antihistamine contains more than one active ingredient, or it contains decongestant medication as well, it isn’t safe for your pup. Some chemicals in human medicines can be fatal if your pet eats them, so always check that the medication only contains antihistamine and follow the advice your vet has given you.
Human medicine will only be prescribed to a pooch if there is no equivalent animal product available. But as long as it has been prescribed by your vet and you follow their advice, it should be perfectly fine for your dog.
If you don’t notice any improvement in your dog’s symptoms, you’ll need to go back to your vet and you might have to try another product on your pup (as we said, not all antihistamines seem to work with every dog!).
You should always ask your vet about what medication you can give your dog because they will tell you what the safest and most effective treatment will be according to your dog’s individual needs. This is especially important if your pooch has any underlying health conditions because some types of drugs could make their illness worse.
If your dog suffers from any of the following conditions, antihistamines might not be safe for them.
High blood pressure (Hypertension)
Antihistamines can also interfere with any medications, vitamins, supplements, or herbal remedies that your dog is taking so remember to tell your vet about everything your dog has.
Never try to treat your dog without the help of your vet because you might make them even sicker.
Piriton is a well-known brand of antihistamine that’s readily available in most supermarkets and pharmacies. It uses the active ingredient “chlorpheniramine” which can be safe for use in dogs. You must only give Piriton to your pooch if your vet has told you that it’s safe, and always use the exact dosage they have recommended.
Benadryl is another brand of antihistamine available over the counter and it uses the active ingredient “diphenhydramine”, which is usually safe for dogs. However, some varieties of Benadryl do use other ingredients which can be harmful for your pooch and giving them too much can be fatal.
We humans usually take antihistamines during the hayfever season to combat sniffly noses and itchy eyes. They can also be used to treat the symptoms of mild allergies, or even to soothe a bee or wasp sting. But in what situations can you give dogs antihistamines?
The most important thing to do if your dog is stung by a bee or wasp is to carefully remove the sting and bathe the area in water. You can also apply ice to reduce the swelling and soothe your pup’s pain and itching.
It is possible to give your dog an antihistamine to help settle their symptoms after a sting. However, you must ask your vet first about what kind of antihistamine is safe for your dog to use, and how much they can have.
Usually if your dog is itchy a few baths with oatmeal shampoo or a medicated shampoo can soothe their symptoms. Rubbing coconut oil on the problem areas can also work wonders.
Your vet might suggest using antihistamines to treat your dog’s itching if it’s related to an allergy, but it will only be part of the treatment plan and not a complete cure.
This is because the only way to treat allergies effectively is to find the cause and avoid it, whether that’s an ingredient in their dog food, a kind of pollen, or even a cleaner you’ve used in the house.
Your vet might advise you to give your dog antihistamines for a little while to help soothe their symptoms while you start investigating what might be causing their allergies. They will probably recommend that you give your dog omega-3 as well to settle their skin.
The number of antihistamines you can give your dog will vary depending on your dog’s size, weight, age, breed, and any underlying conditions they have. As well as your dog’s individual factors, the safe dosage they can have will also depend on what kind of antihistamine you’re using.
For example, antihistamines like Benadryl that use diphenhydramine are usually dosed at 1mg per 1lb of body weight. Meanwhile, medicines that use promethazine are 1mg per 1kg of body weight. Other antihistamines are dosed somewhere between 5mg to 20mg per dog depending on their size.
Additionally, antihistamines can come as a tablet or as a liquid formulation, and each of these has a different dosage. Children’s antihistamines aren’t as strong as the ones made for adult use, so their dosage will be different too.
Liquid formulations can be easier to use for dogs because you can measure the volume more accurately. Children’s antihistamines can also be easier to use with small dogs because they aren’t as strong, so the dosage isn’t as small and difficult to measure.
Your vet will be able to help you to determine the safe dose for your dog. And remember, the dose that’s safe for humans definitely won’t be what’s safe for your hound because they are much smaller than humans and have completely different metabolisms.
Antihistamines can be found naturally in various foods and plants. For example, stinging nettles have an antihistamine effect, but don’t go rubbing them on your pooch or you’ll make them agitated and itchy! Instead, stinging nettle will need to be taken as a tea or a herbal supplement to benefit from the antihistamine effect.
Another natural antihistamine is bromelain which can be found in pineapple or as a herbal supplement and has an antihistamine effect. You might also find a supplement called quercetin which can also be found in apple skin and works similarly. But eating some apple or pineapple won’t fix your dog’s itching because there isn’t enough active antihistamine inside it to help them. Antihistamines as a supplement or a medication are much more effective because the antihistamine has been isolated and concentrated.
Although it isn’t an antihistamine, omega-3 works wonders on many pups with allergies and it’s perfectly safe to use, even if your dog has another condition or medication. Omega-3 can be found naturally in some foods, like oily fish, but it’s also readily available as a safe supplement. Omega-3 doesn’t have an antihistamine effect, but it does have an anti-inflammatory effect and it has a proven benefit for pups with allergies, especially when it’s given to them alongside antihistamines.
Written by: Dr Andrew Miller MRCVS
Andy graduated from Bristol University in 2010 and sees nutrition as a foundation for our pet's wellbeing and takes a common-sense approach. We are what we eat, and it shouldn't be any different for our pets.