Dr. Mark is a veterinarian. He has been working with dogs for more than 40 years.
The Best Antihistamines for Dogs With Skin Allergies
Antihistamines are a type of allergy pill that will sometimes help a dog that has started scratching. As long as your dog has not scratched himself up so much that he is bleeding, an antihistamine will help your dog for the short term until you can visit the vet and find an alternative solution.
This article is not going to offer you a long-term solution to your dog's itching and scratching. That cannot be done over the internet, so you really need to have your dog examined by your regular vet. In the meantime, however, there are some over-the-counter products that may be able to provide your pet some degree of relief. Before we get into them, it's important to discuss safety.
NEVER give your dog an antihistamine that also contains a decongestant. These products may be labeled with a "-D" at the end of the antihistamine name.
I am an advocate for treatment at home. When someone calls me and cannot bring their dog in right away, I try to suggest something that will help the animal feel more comfortable. Antihistamines available at a local pharmacy or drugstore are often the best option.
If you already have antihistamines at home and want to use them on your dog, please be careful. Not all of the antihistamines that are available over the counter are safe for your dog.
If you are using a well-known brand like Benadryl, for example, there are several formulations available. The only product that you should buy for your dog is a simple antihistamine. Antihistamines that include decongestants should not be given to dogs.
A product can be labeled as Benadryl and still contain a decongestant. If the label has a "-D" after the antihistamine name, do not use it. Read the label carefully before giving it to your dog.
Decongestants will make your dog suffer. They can cause your dog to . . .
- “Bounce off of the walls” and become hyperactive and overexcited.
- Collapse due to blood pressure changes.
- Have dilated pupils.
- Have tremors or even seizures.
4 Antihistamines That You Can Give to Your Dog for Itching
- Diphenhyramine (Benadryl)
- Ceterazine (Zyrtec)
- Loratidine (Claritin)
- Chlorphenaramine (Chlortimeton)
(Your vet may suggest other prescription-only alternatives if your dog is put on an antihistamine trial.)
1. Diphenhydramine (Benadryl)
One of the reasons that your dog's skin is inflamed and itchy is histamine, a chemical that causes us to sneeze and causes dogs to itch and scratch. The antihistamines will help reduce the itching so that your dog can scratch less, and rest.
This antihistamine has been around a long time and should be the first thing you try if you cannot get your dog to the vet. It is usually inexpensive if you can find the generic version where you shop, but if you do buy the name brand (Benadryl), make sure not to buy the Benadryl-D. (You should also use only the tablets, not the Benadryl liquid.)
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Dosage: 1–2 mg/kg Every 8 Hours (Three Times a Day)
As long as your dog does not have any other medical conditions, this drug can be given at about 1 mg per kg. (Most vets will recommend twice this dose to start out, about 1 mg per pound, and a slightly higher dose is almost always safe.) It needs to be given two or three times a day, evenly spaced out (about every 8 hours).
If your dog is about 25 kilos (about 60 pounds), you can give him one of the 25 mg tablets. If he is still scratching in about an hour you can give another, but do not give the next dose until 8 hours have passed.
One of the side effects of diphenhydramine is drowsiness. This can be a problem for humans, but for most dog owners this is a great thing. A dog that is miserable and scratching himself raw might get a little sleepy, decide to take a nap, and the histamine will stop being released when the dog stops scratching. No histamine release, less itching.
Note: This drug is very safe and has been used in veterinary medicine for many years. The only known case of toxicity I am aware of was a malicious case in Canada where the dog was poisoned with this drug at 10 times the recommended dose. Even that may not have been enough, and he was also poisoned with ethanol.
Unfortunately, diphenhydramine only works in about a quarter of the dogs that are treated. You need to keep your dog on this drug for at least a week before you decide that it is not going to help. If it does not help, you can try another of the antihistamines but wait until the medication is out of his system in about 8 hours after the last dose.
2. Cetirizine (Zirtec)
If your dog is going to be on an antihistamine trial, and not just a quick something “until I get to the vet,” cetirizine is a great drug to try after a week of using diphenhydramine.
Sometimes it is the best thing to start out with, as it is more convenient since it is only given once a day. Some vets consider it the first antihistamine to try in dogs that cannot be on stronger drugs like steroids.
Dosage: 0.5 mg/kg Once a Day
As long as there are no complicating factors (like pregnancy or disease), your dog can start out at 0.5 mg per kg once a day. (A very small dog will get half of a 5 mg tablet since they are the smallest dose available, but if your dog is larger you can buy 10 mg tablets too.)
- Excessive salivation
Just like with diphenhydramine, you should give this about a week before giving up and moving on to another antihistamine.
3. Loratidine (Claritin)
This is another good option to try for many dogs. It is available in a generic tablet, so it is inexpensive, and if you have allergies, it might already be in your medicine cabinet.
Dosage: 0.25 mg/kg per Day
If your dog is small (less than about 10 kg), you can give him half of one of the small tablets, or 2.5 mg. A medium-sized dog will get about 5 mg, and a large dog will be taking 10 mg a day. (Some vets recommend giving half of a tablet twice a day.)
DO NOT use this antihistamine if your dog has a health problem like liver disease or kidney disease, or if your dog is on medication for some other problem.
DO NOT use this antihistamine if your dog has a health problem like liver disease or kidney disease or if your dog is on medication for some other problem.
- Excited or lethargic
- Dry mouth and dry eye
Try this medication for a week as long as the itching does not become worse and your dog has no side effects. If it is not effective in that time, and your dog has not scratched himself so raw that he has damaged his skin, you can try the next antihistamine.
4. Chlorphenarimine (Chlortrimeton)
This allergy pill works well in humans, and it may also work on your dog. It functions the same way other antihistamines do, by blocking the histamine receptors and is also common in the medicine cabinet of people suffering from allergies.
Dosage: 0.2–0.8 mg/kg Divided up 2 or 3 Times a Day
If you have the 4mg tablets on hand, a small dog (less than 5kg) will get only ¼ to ½ or a tablet. A medium-sized dog will get ½ to 1 tablet two or three times a day, and a large dog will get 2 to 4 tablets two or three times a day.
A lot of the side effects that are listed have only been seen in humans, but it is still a good idea to give as small a dose as possible and not give this medication if your vet has prescribed anything else.
- Appetite loss
- Vomiting, maybe diarrhea
There are also some prescription antihistamines that your vet may want to try. If none of the medicines on this list help your dog, you can discuss one of the other medications.
Are Antihistamines All Your Dog Needs?
In order for your dog to feel relief from his allergies, you need to find out what is causing him to itch. Unfortunately, finding out is not always easy. Antihistamines might provide some comfort at the moment, but they are usually not enough.
Your dog might need a dietary change, a new drug regimen like cytopoint or apoquel, or even a course of steroids like prednisone. Natural alternatives like shampoos, coconut oil, and herbs help some dogs. The best thing you can do is find out what your dog is allergic to and prevent him from accessing it. There are a lot of options.
Can You Provide Itch Relief Without a Pill?
Most of you want to provide your dog with some temporary relief before he scratches himself up and starts bleeding. Giving him a small dose of antihistamines is usually the best and safest way to do so.
If you cannot or do not want to give your dog an antihistamine, the best way to cool off his inflamed skin is by giving him a bath. Almost all dogs will feel better.
- Oatmeal shampoo: Even if it is late at night, you do not need to worry about finding a pet shop to sell you shampoo. Take some oatmeal (the regular kind from your kitchen), put it in your blender until it is fine, and then add water until it is thin enough to use as a shampoo. Oatmeal contains polyphenols and antioxidants called avenathramides that have an anti-inflammatory effect on your dog's skin.
- Plain water: If you do not have any oatmeal, and there is no store around to get any, even plain water is better than nothing.
- Dry bath: Some dogs hate water and will not put up with a bath. If you cannot bathe your dog, you can still use the oatmeal on his skin. After blending, do not add water. Just use the dry oatmeal and apply it to the areas that he has been scratching excessively. You need to leave it on for about 20 minutes before brushing it out.
If you want to do everything you can for your dog, give him the oatmeal bath and then a dose of diphenhydramine. The antihistamines have a better chance of working if the skin is not actively inflamed, and after all of the excitement of a bath your dog may sleep better. Then you can, too.
- Antihistamines in Allergies: Treatment of canine atopic dermatitis: 2015, Olviry, BMC Veterinary Research Journal, 2015, 11 <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4537558/?>.
- Owner assessment of therapeutic interventions for canine atopic dermatitis: a long-term retrospective analysis, Dell, Journal of Veterinary Dermatology, 2012 Jun; 23 <https://www.ncbi.nlm.nih.gov/pubmed/22575021>.
- Treatment of canine atopic dermatitis with cetirizine, a second generation antihistamine: A single-blinded, placebo-controlled study, Cook et al, Canadian Veterinary Journal, 2004 May; 45(5): 414–417 <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC548625/>.
- Benadryl safety: Fatal Diphenhydramine Poisoning in a Dog, Buchweitz J, Canadian Veterinary Journal, 2014 Nov; 55(11): 1089–1092 <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4204843/>.
- Oatmeal shampoo: Safety and efficacy of personal care products containing colloidal oatmeal Maryline Criquet, Romain Roure, Liliane Dayan, Virginie Nollent, Christiane Bertin Clin Cosmet Investig Dermatol. 2012; 5: 183–193<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3508548/>.
This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.
© 2019 Dr Mark
Miebakagh Fiberesima from Port Harcourt, Rivers State, NIGERIA. on March 09, 2019:
Sure; and very informative and education likewise. I hope many dog breeders take note of the contents rightly.
Liz Westwood from UK on March 09, 2019:
This us a very useful guide to antihistamines as well as some alternative remedies.
Miebakagh Fiberesima from Port Harcourt, Rivers State, NIGERIA. on March 09, 2019:
Hello, DrMark, thanks for sharing. Have a great weekend.