Benadryl For Dogs With Mast Cell Tumors: How It Can Help
Updated: January 26th, 2022
Summary
Vets often prescribe Benadryl for mast cell tumors. Why on earth do they do that? Dr. Dressler explains how this common allergy med can help.
Benadryl for mast cell tumors? What on earth does an over-the-counter allergy medicine have to do with cancer?? Let’s find out.
Most of us have heard of Benadryl, the brand name for diphenhydramine hydrochloride. It’s an antihistamine, which means it reduces the effects of excess histamines in the body.
In human medicine, we usually use it for allergies: hay fever, runny eyes, sneezing, and allergic sinus congestion. It is also used for more sudden-onset allergic reactions, including hives, facial swelling and so on.
In veterinary care, we use it to treat things like insect stings, vaccine reactions or other allergic reactions in dogs.
And we often recommend Benadryl for dogs suffering from mast cell tumors.
Dogs with cancer are not experiencing allergies. So, what’s the logic?
Dr. Dressler goes into deep detail on Mast Cell Tumors in his audio seminar.
Well, it turns out there are similarities between a dog with a high mast cell burden and a dog experiencing allergic flare-ups. And Benadryl for mast cell tumors can address those.
Mast Cells Are Weird and Cool
Mast cells are really interesting cells. They are part of the immune system, a type of white blood cell.
Mast cells help rid the body of foreign invaders or material. They also help in healing. They do this in part by generating a substance called histamine. Yup, the same histamine that we talk about when it comes to allergies.
Mast cells that are normal release histamine as part of their work. Histamine helps attract other white cells to trouble spots, like foreign bacteria, or viruses, or injuries. They’re like those red flags your car’s roadside safety kit has. Histamine “marks” an area of the body that is in trouble, so other immune cells can find the area.
Histamine also causes blood vessels to dilate (get larger), and get a little “leaky.” The increased blood flow brings more white blood cells more quickly, and the little leaks help the white blood cells slip out of the blood and into the area that needs them.
So, you see, histamine is an important part of our immune system.
Mast Cell Detects Trouble ==> Releases Histamine ==> Attracting Other Immune Cells ==> Which Kill Invaders and/or Repair Injuries
So, yay histamine, right?
Yes. Mast cells are cool, because they produce histamine. Until they produce too much.
Mast Cells Can Overdo It
As with all things, balance is needed when it comes to histamine. Too much histamine is not good for the body.
When mast cells release too much histamine, whether during an allergic reaction or by huge numbers of cancerous mast cells, bad things happen.
- The blood vessels in the area of the mast cells dilate, bringing inflammation and swelling of body tissues. In allergic reactions, this looks like hives and abnormal swelling.
- The excess histamine is capable of causing the lining of the stomach to produce excessive acid. This causes loss of appetite and lethargy.
- Blood pressure can be affected if enough histamine is secreted. It can drop to truly dangerous levels as many blood vessels open up all at once.
As it turns out, when a lot of mast cells are busy releasing their contents, they secrete lots of things, not only histamine. There are other chemical signals that work in tandem with the histamine, and those get released, too.
The end result of all these mast cells releasing their chemical signals is that the dog’s body goes into a completely abnormal state.
Inflammation and swelling results, and discomfort, as well. I would imagine the sensation is like getting stung or perhaps old stings (itchy, burning). Those with allergies might be familiar with the feeling of all-0ver discomfort, a sort of panicky itchy weird feeling. I imagine it is something like that for our dogs who have a massive release of histamine.
Histamine and Mast Cell Tumors
Now, both cancerous and non-cancerous mast cell tumors are capable of releasing histamine, and both are capable of releasing too much.
If your dog has allergies, you might see a little swelling or redness, and itching. Same is true if your dog has mast cell tumors.
But NOT every mast cell tumor will release very high levels of histamine that cause terrible symptoms like those above.
So if your dog has mast cell tumors, don’t assume that you will see those symptoms.
Only the most severe cases will have these high levels of histamine release.
Why We Use Benadryl for Mast Cell Tumors
Benadryl blocks the effects of histamine in the body, which is why it’s called an “antihistamine.”
Basically, it helps the body cope with abnormally high histamine levels.
That’s why you might hear your veterinarian recommend it for your dog with mast cell tumors: it can help to block the uncomfortable-to-dangerous effects of excess histamine released by cancerous mast cells.
Benadryl can help with the side effects of excess histamine sometimes associated with mast cell tumors.
Remember how excess histamine can also affect the stomach, by causing extra stomach acid? Benadryl helps with that, too. However, sometimes veterinarians will also suggest using an antacid as well, just to be sure to protect the tummy. Cimetidine and famotidine (Tagamet and Pepcid) are often used, and ulcers (if they are present) are often treated with misoprostol (Cytotec) and sucralfate (Carafate).
Please ask your veterinarian for the dose recommendation for your own specific dog and their specific condition.
Diet Matters
If you’ve read my book, you know that I recommend a low-carb, relatively high fat, moderate protein diet for dogs with cancer.
If your dog with mast cell tumors is also experiencing excess histamine release — and remember, not all do — there are special dietary considerations you should also be aware of. You can read more about special nutritional choices for dogs with mast cell tumors in this article.
Of course, diet is just one of five steps in my Full Spectrum approach to cancer care. In addition to diet, nutraceuticals, anti-metastatic supplements, and mind-body strategies, you can find an entire chapter on the conventional care for mast cell tumors in chapter 30 of The Dog Cancer Survival Guide.
All my best,
Dr D
If your dog has mast cell tumors, this book is a wealth of information. In addition to the main steps Dr. D recommends, read the extra chapter dedicated to mast cell tumors from Dr. Ettinger, his oncologist co-author.
Dr. Demian Dressler is internationally recognized as “the dog cancer vet” because of his innovations in the field of dog cancer management, and the popularity of his blog here at Dog Cancer Blog. The owner of South Shore Veterinary Care, a full-service veterinary hospital in Maui, Hawaii, Dr. Dressler studied Animal Physiology and received a Bachelor of Science degree from the University of California at Davis before earning his Doctorate in Veterinary Medicine from Cornell University. After practicing at Killewald Animal Hospital in Amherst, New York, he returned to his home state, Hawaii, to practice at the East Honolulu Pet Hospital before heading home to Maui to open his own hospital. Dr. Dressler consults both dog lovers and veterinary professionals, and is sought after as a speaker on topics ranging from the links between lifestyle choices and disease, nutrition and cancer, and animal ethics. His television appearances include “Ask the Vet” segments on local news programs. He is the author of The Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog’s Life Quality and Longevity. He is a member of the American Veterinary Medical Association, the Hawaii Veterinary Medical Association, the American Association of Avian Veterinarians, the National Animal Supplement Council and CORE (Comparative Orthopedic Research Evaluation). He is also an advisory board member for Pacific Primate Sanctuary.
Dr Dressler
I have a 10 year old Rottweiler named Misty She was recently diagnosed with hip dysplasia and Cancer in her Back Knee Joint. She is currently on Tramadol 50 mgs for pain twice a day however I have no idea how much pain she is still in and if she needs something stronger? I have some 325mg percocet which I believe is stronger but have no idea if it is safe for dogs and how much she would need, she weighs about 65 pounds. My husband recently lost his job and I cannot afford another vet bill but I’d like to keep her comfortable. She has cut back on eating so I think that might be a sign she is hurting more. Her knee is getting quite swollen probably twice the size of the other knee. I am also at a loss as to how long her go like this before I have to put her down as I don’t want her to suffer too much! I would appreciate any advice you could give me!!
Please let me what you would recommend?
Thanks
Julie Marmolejo
Dear Julie-
most vets will do a phone call for free, and can work with you to get some good dog medication on board. Some vets also take care credit. Check out this post:
https://www.dogcancerblog.com/blog/the-cost-of-my-dogs-life-part-1/
I hope this helps.
D
Dr. D,
I’m curious how much benadryl you should give for mast cell tumors and for what duration? We have a 7 year old pug who weighs 25 lbs and has been diagnosed with mast cell tumors. A few months ago, we had 6 tumors surgically removed, and at that time our vet did mention benadryl, but did not give specific informtion on dosage or duration. Last night we noticed another small bumb starting to grow, so we wanted to get him started on the benadryl. Could you please help? Thanks!
Sincerely,
Rachael
Dear Rachael,
I would check with your vet, who knows whether there might be some problem with the benadryl or not. Always work with vet supervision. The dose for benadryl is 1 mg per lb 2-3 times daily, so that would be 25 mg. But check with your vet. I would also suggest Apocaps to stabilize the mast cells.
Best,
D
My Minnie Mouse has been fighting mast cell for over 3 years. I have only had 2 needle aspirations,mainly to prove to the vet that those wart like growths WERE mast cell. I have removed over 14 small growths,have several in a jar,but I haven’t been able to reach all of the original ,larger tumor,thought I had it but after a year it came back. I have found another weapon tho,lutimax(strong luteolin) the tumor that came back has shrunk to about 1/3 of it’s size,I am giving 3 per day,using benedryl & tagament(has anti cancer properties). I am not sure how it works,please Dr Dressler,expound a little on this lutimax for us,I am very excited & Min is feeling better. Her first treatment was Aug. 1,2007,so it has been a long fight,overall tho,good QOL 🙂
Dear Patsi,
great question. Luteolin can benefit dogs with mast cell tumors in my experience, as you have found as well. I am glad it is helping your Minnie Mouse! It is for this very reason that I included it as one of the compounds in the formula created for my patients (Apocaps), in addition to other potent compounds that have shown to act with luetolin to help these dogs. If you would like to read more about lueteolin specifically, check out this post. and this one too.
Best,
Dr D
Dear Harvey,
Thanks for your comments. Benadryl can help decrease the effects of the histamine which is produced by the mast cell tumor, and is definitely a good idea. I should make clear that it does not stop the cancer from spreading though…But thank you for your kind words and I am so sorry for little Roxy.
All my best,
Dr D
Hello, we are proud to have an 8 year old Blue Nose APBT. We saved her life by adopting her from the pound. Six years ago we had 3 large tumors removed one of which came back 6 months ago. They were found to be mast cell one being a stage 4. A few months ago a few more came back and we also had thos removed. Since then no more have shown up, my concer is that I want to know whats happening inside her. She eats like a pig and still loves to run and play. She does suffer from arthritis and I would like to know how to treat that without upsetting her stomack. Thanks for all the helpful information and I’m so sorry for the Harvey’s loss of their beloved pet.
Sincerely,
Nicole Pinckard
Dear Nicole,
you raise a very good point. Dogs with cancers like your dog’s should have regular ultrasounds done to assess the internal organs, with blood and urine testing, every 2-4 months as directed by your vet. Please be sure to have your vet supervise all of your dog’s treatments. In my patients I prescribe Apocaps. I would really pay attention to her diet (you can download the Dog Cancer Diet pdf on the top of the blog page). Finally, there are many other things to consider (so many that it filled a book), so I would really take the time to get and read The Dog Cancer Survival Guide. It is easy reading and will help a lot.
Best,
Dr D
Harvey, I am so sorry to read about your tragic fight with Roxie. My Husband and i had a similar situation with our 5 1/2 year old Golden Retriever named JOSIE. Our fight began in May with her first operation and a second one in the beginning if June. The vet didn’t aspirate the 3 tumors so he didn’t know that he was removing mast cell tumors. Three weeks after her second operation we went to an oncologist who gave us the horrible news that Josie’s cancer had spread to the lymph nodes and we had little time with her. She died August 19,2010. Just 54 days after the oncologist informed us of her grade three mast cell cancer. Our vet did not tell us that her cancer was deadly and we lost some valuable time in the beginning and were literally online gathering information day and night to fight or slow down the progression. It’s a shame that there is nowhere we can go to receive the correct protocol for this cancer.I learned of the Morris Animal Foundation after my Josie was gone. Hopefully someone reading this can pass the name along and help someones pet. They do alot of research on Canine Cancer and help sponsor fundraisers for research dollars. Again, I am sorry for your loss! Donna
Dr. Dressler,
You are so right in the use of Benadryl involving a mass cell tumor. My 12 year old Pug named Roxie had a growth on her side 2 months ago. My vet sent me to a “special” vet hospital for the removal of the growth. They removed the growth then tested it finding it to be a mass cell tumor. Within a two month time period the tumor came back 5 times the size with other tumors also appeared on her body. Soon she started to cough alot and was in great pain and the tumors started to bleed.. She was a sweet loving animal and she lost her fight on 10/04/10. While reading up the causes and treatments for mass cell tumors I found out that the “special” vet hospital NEVER gave my dog any type antihistamine prior to or during the operation. The operation acted like a bomb sending the cancer through out my poor little girl. The information you provide to your readers is very imformative and helpful, I just wish I found you 2 1/2 months ago. But I do have two other pets at home, a boxer and another Pug so thanks to you I am better prepared in case this horrible thing happens to then. So all you other pet owners out there please speak up for your animals, ask the vet questions and take them to a CANCER VET Hospital. Just don’t think your vet is a “Jack of all trades” and knows how to treat cancer.
Again Doctor thank you!
Harvey
Hello Dr Dressler,
I hope you won’t mind but I have another question. I have been reading a lot about Benadryl & MCT. When giving the Benadryl tablets should you also give something like Zantac or Pepcid as well. Tagamet is not available OTC in the UK.
Many thanks
Susan
Hello Dr Dressler,
My dear Golden Retriever Penny has mast cell tumours. One was removed in 2008, another 6 months ago.Two nights ago without any warning another erupted & busts needing emergency surgery. Whilst she was under the anaesthetic the vet took the opportunity to remove 2 more that we had been wtaching for months as well. I have read with interest about Benadryl. I want to start Penny on it. My vet was not very encouraging & pretty negative about it but I feel more that it was because it was my suggestion & not his ! He has told me to give her one in the morning & one in the evening. Please would you advise me on this . Many thanks
Hello Dr Dressler–
I have an 8 yo female lab/redbone mix. She has had a medium sized lump on her belly area (near her nipples) for a little over a year. It has not changed in size and she as no related symptoms (appetite is fine, no itching, no vomiting, no pain. She is as happy, hungry and loving as she has ever been!). I was recently told it was a mast cell tumor. Due to recent divorce and job loss, I cannot afford the surgery to have the tumor removed. Are there any alternative options or suggested treatments other than surgery–should I be giving daily benedryl… if so, how much? What should I expect if I am unable to treat this tumor?
Thanks,
Cindy