Featuring Demian Dressler, DVM and Susan Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide.

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Why Benadryl For Mast Cell Tumors?

Most of us have heard of Benadryl.  In human medicine, we usually use it for allergies.  You know, hay fever, runny eyes, sneezing, and allergic sinus congestion.

It is also used for more sudden-onset allergic reactions with hives, facial swelling and so on.

In veterinary cancer care, Benadryl is often recommended for dogs suffering from mast cell tumors.

Since these dogs are not experiencing allergic reactions, what is the logic? Well, there actually are some similarities between a dog with a high mast cell burden and a dog experiencing allergic flare-ups.

Here is how it works.

Mast cells are a type of white blood cell in the body.  They normally operate to help rid the body of foreign invaders or material. They also help in healing.

These cells contain a substance called histamine.  Yes, just like the root of the word antihistamine. Both cancerous and non-cancerous mast cell tumors are capable of releasing histamine.

Histamine is useful in the body at certain levels.  Mast cells release histamine which helps attract other white cells to an area or an invader to help clean up the area, or mount an immune system reaction.

Histamine causes blood vessels to dilate (get larger) and get a little leaky. This lets more white cells and blood flow into an area.  The leaky parts let white cells slip out of the vessels to get to the site of injury or invader.  Histamine is important in immunity.

However, too much histamine is not good for the body.

When too much histamine is released by mast cells in the body, whether during an allergic reaction, or by huge numbers of cancerous mast cells, bad things happen.

As it turns out, when a lot of mast cells are busy releasing their contents, they secrete a lot of things.  Histamine is one of them. There are still more chemical signals that work in tandem with the histamine.

The end result of all these mast cells releasing their chemical signals is that the dog’s body goes into a completely abnormal state.

The blood vessels in the area of the mast cells dilate. Inflammation and swelling of body tissues accompanies the release of mast cell contents. Discomfort results as well. I would imagine the sensation is like getting stung or perhaps old stings (itchy, burning).

The excess histamine is capable of causing the lining of the stomach to produce excessive acid. This stomach acid contributes to the loss of appetite and lethargy seen in some cases of mast cell cancer.

If enough histamine is secreted, the blood pressure can drop due to dangerous levels.  This is because massive mast cell activity causes many blood vessels to open up, which is causes the pressure in the vessels to drop.

Of course, we must recall that there are many different forms of mast cell tumors with different behaviors.  Only the most severe ones will have these levels of histamine release.

Benadryl is useful in blocking the effects of the histamine in the body. It’s antihistamine effect helps the body cope with these abnormally high histamine levels.

In addition, the antacids cimetidine and famotidine (Tagamet and Pepcid) are often used in dogs to block the excess acid secretion caused by the histamine excess. Ulcers are often treated with misoprostel (Cytotec) and sucralfate (Carafate).

Other aspects of conventional care for mast cell tumors are found in The Dog Cancer Survival Guide.

All my best,

Dr D

About the Author: Demian Dressler, DVM


Dr. Demian Dressler, DVM is known as the "dog cancer vet" and is author of Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog's Life Quality and Longevity. Visit his blog and sign up free to get the latest information about canine cancer. Go to http://www.DogCancerBlog.com.

  • Cindy

    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

  • Susan Hickman

    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

  • Susan Hickman

    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

  • Harvey

    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

  • Donna Walker

    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

  • Nicole Pinckard

    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

    • http://DogCancerBlog.com DemianDressler

      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

  • http://DogCancerBlog.com DemianDressler

    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

  • patsi

    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 :)

    • http://DogCancerBlog.com DemianDressler

      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

  • Rachael

    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

    • http://DogCancerBlog.com DemianDressler

      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

  • Julie Marmolejo

    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

  • Shawn

    Hello,

    I brought my 3 year boxer to the vet to look at a small growth on the inside of his ear and wanted the vet to aspirate to ensure it was not malignant. Before the vet tried to aspirate it, she gave him an injection of benadry. What would the purpose of giving benadryl prior to knowing exactly what type of growth it was? Thanks for your help with this.

    Respectfully,

    Stitus

  • Tammi

    Dr. Dressler,
    My dog was diagnosed with Osteosarcoma about 3 months ago. I was wondering if I can give him the Apocaps? He is currently on pred, sucralfate, and tramadol. Thank you for all your research.
    Sincerely,
    tammi

    • http://DogCancerBlog.com DemianDressler

      Dear Tammi,
      sorry to hear about your dog :(
      I use Apocaps routinely in dogs that have osteosarcoma. If you are using pred, cut the labeled dose down to half on the Apocaps. Of course you want to always have your vet involved in any steps in your dog’s care.
      Best,
      Dr D

  • Lisa Richards

    Dr. D.
    I will get your book, it sounds like it has good information. I had a question if you have time. My 10 year old lab was tested positive for mast cell. We removed bumps. 3 months later more came back. We removed them again. 2 months later tested positive again. Went to oncologist who advised to remove the cancerous bumps and start chemo. We removed them 2 days later, they all came back “negative” for cancer! This third surgery was tough on her and to find them all negative made no sense and doctor couldn’t say why that happened. My dog has been on benadryl, pepcid ac, and prednizone for 4 months. Nothing has returned, they say take her off all meds. Is there any benefit to staying on bendaryl and pepcid ac to prevent it from coming back?

  • Cindy

    How long should you keep giving the dosage of benadryl twice a day. My dog is close to 100 lbs.

  • Nancy

    Hello Dr. D,

    I have a question I can not find the answer to. I have a 4 1/2 year old pug who had a mast cell carcinoma removed from his side in April, 2010. After the first surgery we were told that his margins were dirty and that he would need more surgery, A week later they removed more tissue and we were told that his margins were clean. A few days ago without any notice, he developed hives all over his body and head. His face and snout was very swollen. We rushed him to the vet and they gave him an injection of benadryl and a steroid. We were told to give him benadryl 25 mg 3 more times. Today he seems fine, however, we have no idea what happened, Do you think this could have happened due to a recurrance of the mast cell carcinoma or just some allergic reaction. I do not seem any lumps on his body. The vet that treated him is not our regular vet and did not know his history of the mast cell carcinoma.

    Any suggestions or information would be greatly appreciated

    Thank you.

  • Susan

    Dr. D.
    I hope my post helps someone. Our 6 year old redhead longhaired chihuahua has had 2 malignant mast cell surgeries. They have been stage 2. After her second surgery, I read about Bendryl and discussed it with our vet. He said to try it. Every morning we give her 2 mg of children’s storebrand Benadryl and so far she has done well. She had surgery about 2 months ago on a suspicious growth, but it was benign which was encouraging.
    Thank you so much for your information!!!!!

  • Kevin

    The vet has me giving my dog benadryl to treat his nasal-cancer-like symptoms along with prednisone. He’s had 2 nosebleeds, constant nasal congestion and for 1 he had a half-dollar sized lump on his nose. He gets worse when I run out of benedryl and only gets better when I get more. Could it be possible that this isn’t cancer? I haven’t been able to get xrays done because of financial difficulties and because I’m hesitant to have him put under and out of my sight all day while he recovers from the anesthesia. I’m not trying to get my hopes up because hope is a heavy burden for me right now. It’s easier to accept his fate than it is to deal with the ups and downs of hopelessness and denial.

  • Kevin

    Type-o : he had the lump for 1 day.

  • Nelda

    My 10 year old dog Ellie has been to the vet numerous times since July. She has nasal congestion, mucus running from her nose (at times it was bloody) and she just snores and makes all types of noises. We did have her nose scoped and the Vet could not find anything. We have tried many antibiotics and none worked.The vet gave her a Prednisone short just 7 days ago, and it only worked for a few days and now she is back to be stuffed up sounding and mucus running out of her nose.(no blood yet). Can I give her benadryl too? He believes she does have a tumor but we can’t afford to have her checked further. Will the Apocaps work for this? I need help and suggestions guys. My vet of course probably will not recommend anything since we don’t know EXACTLY what type of tumor is in her nose…the prednisone does seem to shrink it when she first got the shot..it just didn’t last. We do know it is the nose since her trachea and everything else looked fine.

  • maddy

    Need to make comment to get newsletter :) Thanks for all the great info.

  • Danielle

    Our Dog Roxi is a 96Lb American Bulldog. She is all white in color & has alway had allergy problems. She was diagnosed w/ Mast Cell Tumors about 3 years ago. Each day has been different for our girl. One day she is GREAT w/ no bumps, redness or irritation. Other days she will flare up w/ Large (cyst like) bumps all over. Mainly on her hine legs, rear end & belly just under the legs. She has had flare ups before that seemed to go away w/ Benadryl, prednisone & sometimes w/ antibiotics. This time however… She seems like nothing is working. She has been vomiting (which she usually doesn’t do) all day. He belly that has the cysts seems to want to burst open. She has had this happen in the past, but the cyst/group of many cysts is much larger. We recently gave her Echinacea along w/ licoric root. Would this cause her to be upset to in the stomach? We are worried about our girl & just want her to be okay. Does anyone have any advice on how to help her w/ the nausea and or Mast Cells? I’ve called our local vet, but they are out till Monday. Your advice it appreciated! :)

  • Lakisha

    Hi Dr. D!

    Thanks for the helpful information. I have a 7 year old cockpoo that just had a grade 3 tumor removed. My vet referred me to a onologist and she suggested radiation and chemo. The onocologist also did an ultrasound and it seems as though the cancer has not spread. We’ve changed her diet and started her on Benadryl and other supplements. Do you have an other suggestions? Is there more we shold be doing?

  • Kevin

    Hello,

    We have a 14-yr old female Yorkie-Poo that has a mast cell tumor on her right rear paw (right between the far-right digit, and the next one in). It is quite large and steadily growing. We are working with an oncologist, and she is on chemo; however, it has not worked. The tumor is still growing, although it is currently not bleeding. The tumor is already in her lymph node higher up on her leg. She has her ‘spunk’ and is eating well with no signs of pain.

    We have been given two options: 1.) Surgery to remove either part of her foot, or her entire leg, or 2.) Let her live out her remaining time.

    What should we do? Do people normally have surgery on a 14-yr old dog? Will she survive the pain and healing?

    Or do people normally let her live out her time? What type of phases would a dog normally go through from here on out? When would we know when to put her to sleep so she doesn’t feel any pain (from ulcers, etc.)?

    Thanks for any help or insight into this difficult time.

    • Dr. Demian Dressler

      Dear Kevin
      If the conventional options are not working well it would be good to use some other tools. Have you read the Guide yet? I’d be thinking diet, apocaps, low dose oral neoplasene with mirtazapine, possibly palliative radiation…as some first thoughts. You could also consider a different chemo drug (switch from palladia, kinavet,or use the injectable drug protocols etc)
      I would discuss these options with your vet, or for integrative vets perhaps contact the veterinary institute of integrative medicine, or the American Holistic Animal Association.
      Here is another link or two I wrote that might help too:
      http://www.dogcancerblog.com/an-overview-of-what-else-can-i-do/
      http://www.dogcancerblog.com/what-is-treatment-plan-analysis/
      I hope this helps
      Dr D

  • Denise

    Dear Dr.,
    My 10 year old, Auusie Shepherd, has been developing lumps from his chest to his back legs. He has several on his rib cage and around his leg bones at the shoulder joint. Vet isn’t worried, but his appetite is starting to lessen and he is always ready for a nap. Would the use of the antihistamine possibly work for him?

    • Dr. Demian Dressler

      Dear Denise
      my feeling on this is that you should be in contact with your vet about the cause of the bumps. If they are hives (allergic), then antihistamines can help in some cases. But it is very important to determine whether there is an allergic issue occurring, and also why your Aussie is eating less. The bumps may or may not be related to the loss of appetite. That way you can provide the proper care for the actual issue.
      I hope this helps
      Best
      Dr D

  • Jacqueline

    Hi Dr D

    My dog has a small pea sized lump in his skin. We had the needle aspiration done yesterday and it is a MCT. My boy is 10 years old and such a happy dog that I really don’t want to have him operated on (I am also worried about the effects of anesthetic on him as he is a French Bulldog, has never been operated on and has breathing difficulties) Is it possible that the lump may just stay the way it is and have no detrimental effect on his life? I am planning to start him on prednisolone tonight. Am I doing the right thing – or is removal of the lump the best cause of action?

    • Dr. Demian Dressler

      HI Jacqueline. The short answer is wide excision is best. Mast cell tumors in dogs sometimes are life threatening and are never good.
      I would also start thinking about the rest of the body…here’s a post for you:
      http://www.dogcancerblog.com/an-overview-of-what-else-can-i-do/
      I hope this helps…
      Dr D

  • Michael vaughn

    My dog is 13 yrs old and has been getting these tumors of some sort but she busted one and she’s running a fever and acting abnormal. Please reply ASAP

  • Cinny

    My vet also recommended ginger and turmeric caps as supplements to my raw food/probiotic enhanced dog diet, and benedryl when turmors are in early stages of inflammation. We do a few days of prednisone when a tumor is raw and red. This seems to settle the histamines down. My 6 year old boxer has been in great shape for 10 months since he was first diagnosed with stage 2 and had one surgery. I have also added esciac caps.

  • olive

    My little Lu is on her second tumor. She’s 7 years old and both tumors have been in the same spot – her neck. This time the tumor is literally directly beneath the scar from her last surgery. I am giving her benadryl twice a day and I give her pepto when she vomits. If she is too active, she vomits and has diahrea. If she has this next surgery, what is her life expectancy???

    • DrSueCancerVet

      Hi Olive,
      I am sorry about Lu’s MCT, but remember these are generally very treatable tumors, and one size does not fit all – so no one can tell you thru the web what her life expectancy is.
      I would stronlgy recommend you see an oncologist who can examine Lu, review her records, and make recommendations to find out if the tumor has spread and recommend treatment options.
      Also check out my series on MCT – lots on info there, but see a specialist too!
      http://www.dogcancerblog.com/the-oncologists-thoughts-on-mast-cell-tumors/#.UkjXwee9KSM
      All my best, Dr Sue

  • Susan Kazara Harper

    Hi Olive, There’s no way to predict in this format a life expectancy for Lu. It depends on so many factors including type of cancer, staging, whether any other body systems are affected, her immune system, nutrition etc. Your best advisor is your own veterinarian who knows Lu and what she’s been through, and knows you as Lu’s carer. I hope you have read The Dog Cancer Survival Guide and have implemented the Dog Cancer Diet. Nutrition and emotional support are vital. If your vet has prescribed the Benadryl (which makes me think she has been diagnosed with MCT?) then give all of her symptoms to your vet and inquire how you can help her with the nausea. Above all, please don’t focus on “how long does she have’. Make the most of every day and keep Lu happy. She’s living in the moment and is not worried about the future. It’s a lesson we can all take to heart. All the best.