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

Mast Cell Tumor Surgery and Benadryl

Updated: December 12th, 2018

The mast cell tumor is very common in the Pug, Boxer, Rhodesian Ridgeback, Shar-Pei and other breeds.  This tumor most commonly occurs in the skin as a raised, inflamed nodule or mass. Sometimes it is found internally in the liver or spleen.

The cells that make up this tumor are called mast cells.  There are some unusual aspects of these cells that should be paid attention to.

First, they secrete a substance called histamine, which most have heard of in the word “antihistamine”. Histamine is released in the body during allergic reactions and it causes some nasty things. First, histamine causes inflammation, which is no fun for anyone. Redness, swelling, pain… all parts of inflammation.  If you squeeze a mast cell tumor, many will create a red, swollen effect due to the histamine that gets liberated.

Histamine can cause serious harm to the body when released in larger amounts.  When a dog experiences massive histamine liberation, her blood pressure can drop through the floor, causing life-threatening shock.  No blood pressure, no blood getting to vitals like the brain and kidneys.  Bad news.

Imagine if you were to do surgery on a mast cell tumor loaded with histamine.  This is more than just squeezing it, folks. We are talking scalpel action, along with some pulling to free up the mast cell tumor. Imagine the amount of histamine that could be released.

So, it is wise to make sure your vet is on the ball.   Since doing surgery on some mast cell tumors can result in shock, make sure you double check that your dog gets an injection of Benadryl before surgery.  This can block the effects of massive histamine release. Also allow your vet to place an IV catheter and deliver IV fluids or meds during the procedure to keep the pressure up.

Dog cancers are all different.  Each tumor in dogs behaves differently and needs it’s own special treatment.

Stay tuned!


Best to all,

Dr Dressler


Leave a Comment

  1. Susan Kazara Harper on June 23, 2015 at 8:06 pm

    Tanya, This reply is late, but you will get no bashing here. What did the vet day?

  2. Tanya McCollum on May 28, 2015 at 6:04 pm

    I have an American Bulldog. She had a tumor removed from her chest about a month ago. The incision healed up perfect. The vet said the majority of the tumor was benign but it did have a little bit of cancer cells in it. She said that it was grade 1 . Anyway she has started developing blood blisters on her back side and on her belly and by her front left leg( like what would be her arm pit) . They are bleeding constantly and not clotting. She is dripping blood everywhere. I have tried to bandage them up. I am calling the vet tomorrow, I was just wondering if anyone had any thoughts on this. Please don’t bash me. I am calling the vet. I love my dog very much. She is 8 years old and about 105 lbs. She doesn’t chew on her blisters or anything they just keep bleeding. All the hair has come off and they look really sore but she does let me touch them to try to bandage them. Thanks

  3. Susan Kazara Harper on December 7, 2014 at 10:49 am

    It’s scary and a big responsibility, but you are your dog’s champion. Trust that you will know what he wants and that whatever you decide will be the most loving thing you can do to help him. Every dog is different. While you have him, focus on the joy of each day together. Check out and work with your vet. Give him the best, real foods you can, and know that some days he may want to be fed by hand, which is such a loving thing to do anyway. He will tell you each day how he is. Dont’ stop play, which is his joy, but you may need to modify it. Roll the ball to him instead of making him chase it. It’s all good. Check out
    All the best to you both Chris.

  4. chris on November 24, 2014 at 12:39 pm

    I was wondering my dog has the same symptoms as your dog,and they also told me 4 to 8 weeks,, what should I expect toward the end or when I have to put him to sleep … im scared of losing him thanks

  5. Susan Kazara Harper on September 8, 2014 at 1:31 pm

    Hi Debra,
    I’m sorry about your girl’s diagnosis, but you stay strong, OK? It’s great that you’re seeing an oncologist. If she is itching, then an antihistamine like Benadryl could be a good idea, but 1) consult with your own vet about this, and 2) don’t just give her an antihistamine if she’s not having itchy symptoms. When you see the oncologist you want to get the grade and stage of the MCT, as that information will go a long way to helping you decide on treatment. If your girl does get itchy, take a look at …. it’s a blog which works on top of the Dog Cancer Diet to further restrict foods which may make itching worse. But again, don’t go there unless she needs the extra help. No need to make things more difficult. The Dog Cancer Survival Guide has a great chapter on MCT; well worth reading, especially if you can get it before your appointment. Don’t hesitate to get in touch if we can help in any other way. We will all keep fingers and toes crossed for a good appointment. Stay strong, stay happy with your girl, because that’s what she’s concerned about every day.

  6. Debra Armbruster-sells on September 8, 2014 at 6:32 am

    Dr. D my 7 yr old boston terrier has had 2 surgeries to remove tumors the last groin mass path was lymph node mast cell tumor. We are seeing an oncologist next week and I’m very concerned since she now has multiple skin lesions, cysts around her anus and a lump adjacent to her surgical scar. Should I be giving her benedryl until she’s seen it seems these tumors are growing fast she weighs 28 lbs. she is my baby and I will do all I can to help her. Deb

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