Growing body of research says dogs really can smell cancer
August 17th, 2011
07:00 PM ET

Growing body of research says dogs really can smell cancer

A new study adds to the body of research suggesting that "man’s best friend" may actually be able to smell cancer.

Researchers in Germany found that dogs were able to pick up on the scent of organic compounds linked to the presence of lung cancer in the human body, and that their keen sense of smell may be useful for the early detection of the disease.

Four family dogs – two  German shepherds, one Australian shepherd and one Labrador retriever – smelled test tubes containing breath samples of 220 patients, both those with lung cancer and those without it. The dogs were trained to lie down in front of the test tubes where they smelled lung cancer and touch the vial with their noses. According to the study, the dogs successfully identified lung cancer in 71 out of 100 patients with the disease.

And that’s not all. Researchers also tested patients with chronic obstructive pulmonary disease. “COPD is quite common in patients with lung cancer and we were not sure if the dogs could tell the difference between both diseases,” explains Enole Boedeker, an author on the study who practices general thoracic surgery in Stuttgart, Germany. “The dogs could recognize the cancer sample as easily as between the breath samples of the healthy study participants,” Boedeker says. The study is published in the European Respiratory Journal.

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This isn’t the first study to use dogs’ heightened sense of smell to identify disease in humans. Over the years researchers have theorized that cancer may actually have a detectable scent - cancer cells may produce chemical compounds that circulate throughout the body and can be breathed out of the lungs in a gaseous form. The use of canine scent to detect these compounds has shown promise in sniffing out breast cancer, bowel cancer, colon cancer, COPD and lung cancer, and even type 1 diabetes.

“This is probably the most sophisticated study I've seen on this topic,” says Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. Lichtenfeld has been following research on sniffer dogs and blogged about the topic for ACS. “More and more studies are reinforcing the possibility that this is very real,” he says.

But don’t expect to see Fido in the office the next time you visit the doctor; the future clinical implications remain unknown.

“We've seen this happen enough to suggest there are compounds in the breath of patients with cancer that could provide an early warning about he presence of cancer in the body, but we still do not know exactly what those compounds are,” Lichtenfeld says. “We can’t pick out what the dogs smell.”

Researchers say sniffer dogs are a promising “detection device,” but more studies are needed to help identify the specific detectable markers in order to create screening methods.

“Unfortunately,” the study authors conclude, “dogs cannot communicate the biochemistry of the scent of cancer.”

soundoff (344 Responses)
  1. Andy

    It appears most of you come here to make cynical comments about an intriguing and heart-warming story. Congrats. You're not clever. Now go do something productive with your life.

    August 18, 2011 at 16:25 | Report abuse | Reply
  2. Andy

    @Howie...I like dogs much more than I like you.

    August 18, 2011 at 16:26 | Report abuse | Reply
  3. Piper

    Maybe we should send this information to China and these Muslim countries. China eats and skins dogs alive and the Muslims just kill them. Maybe this will teach them that the dogs are probably smarter than they are.

    August 18, 2011 at 16:31 | Report abuse | Reply
    • JeramieH

      Would America stop eating beef if they found an anti-cancer compound in cows?

      August 18, 2011 at 16:43 | Report abuse |
    • Herpaderp

      They kill wild dogs there because they don't have the medical technology to deal wtih rabies and the plague.

      August 18, 2011 at 17:00 | Report abuse |
    • Amir

      It is because of people like you that give Americans the stereotype of being ignorant idiots.
      Your comment lacks even the most basic form of intelligence. Please keep your racist remarks to yourself.

      August 18, 2011 at 17:14 | Report abuse |
    • oe

      It's got to be his 'tea'.

      January 26, 2012 at 04:29 | Report abuse |
  4. Boris

    From collection:



    August 18, 2011 at 16:55 | Report abuse | Reply
  5. iamthefredman

    Wow. 71% success in finding cancer in minutes. Doctors have a 50-60% chance of finding cancer in weeks and months of painful, grossly expensive tests. Hmmmmmm.. Goodbye doctors.

    August 18, 2011 at 16:55 | Report abuse | Reply
    • john

      The doctor's tests are meant to determine exactly what form of cancer it is, how dangerous is, how far it has spread, and how it can be treated, and what the prognosis is. The dog is not telling us any of this, and we don't even know if this is real. One study doesn't prove anything. Maybe the dogs are just smelling the remnants of cigarette smoke, which causes 70% of lung cancers?

      September 15, 2011 at 12:55 | Report abuse |
  6. Cindy

    People can smell cancer, too. I know there have been 3 times when I smelled it on people who were diagnosed soon thereafter. Sometimes I can smell it when I pass people in stores and such. It makes me feel bad that there's no socially acceptable way I can tell them to go to the doctor. Besides, if I'm wrong, I don't want to scare somebody.
    I have a weirdly developed sense of smell though. My family calls me the "bionic nose". ha ha

    August 18, 2011 at 17:18 | Report abuse | Reply
    • Jim K

      It's long been known that many skilled diagnosticians among doctors used to rely much more on their sense of smell – and that some were much better at it than others. But that as more walls, procedures, tests and bureaucracy has been placed between pts and doctors this has become all but a lost art (- except perhaps among some veterinarians).

      Touch is another important diagnostic tool that's being left by the wayside. Almost all direct touching in most routine doctor's office visits is done by nurses, PA's and techs and your doctor may not touch you directly at all.

      It would be great to see dogs used as an humane, fast, cost-effective way to bring back and even improve utilizing on this readily available set of diagnostic cues (i.e., the odors produced by various maladies). Even if only as an initial screening for deciding on whether more extensive/expensive/invasive tests were necessary.....

      August 18, 2011 at 18:09 | Report abuse |
    • Fiona

      I can tell when my dogs are unwell by changes in their breath and skin odor. I've taken dogs into vets' offices and told them that I knew soothing was wrong, had a vet dismiss this and say the dogs were fine, and then (sadly) been proved correct when the dogs became quite ill. I have been able to smell when children are ill. I do believe that some cancers have a smell that is detectable to the human nose, whether because of the cancer cells or the death of cells in the body. When my father was dying of cancer, he had a peculiar odor that was not medication. Have you ever noticed that healthy, fit people smell "clean" even when working out hard, sweating profusely? Of course a creature who is hundreds of times more sensitive to smell can detect diseased tissue, just as they can detect low blood sugar in diabetics or oncoming seizures in epileptics.

      August 18, 2011 at 23:27 | Report abuse |
    • Fiona

      ...something was wrong...

      August 18, 2011 at 23:29 | Report abuse |
    • Kay

      @Cindy: Yes, I too have been able to smell cancer on people since 1975. I was working on a cancer floor in a hospital at the time and no one else claimed to be able to smell it but it is a distinct sweet sickening smell. I am also very sensitive spiritually on many levels and ways. I've been having issues with my right ovary lately and this morning when I awoke I smelled it on me. I will get all the tests in time but I think it safe to say I probably have cancer. In some ways, it is a blessing to have this gift. Please get back with me, as it would be great to know someone else with this gift.

      October 14, 2011 at 07:34 | Report abuse |
    • believes you!

      My father and I just met a man who claims the same thing. He felt free to share because we are First Nations and have not fully lost the connections that modern eurocentric thinking is just beginning to consider. Please share your gift with a First Nations person/healer, or some earth-based people to learn more about your gift:) the man we met was Indian (from India in origin). Thanks for posting!! I am excited about this topic!

      April 20, 2012 at 19:22 | Report abuse |
  7. Santa Claus

    Dogs taste good, I don't see the problem with eating them.


    I have a pet Cow named Betsy, yet everybody eats hamburger and drinks milk. I don't get all bent out of shape.

    August 18, 2011 at 17:18 | Report abuse | Reply
  8. knup

    is it a biochem marker they are smelling, like something un-healthy? or is it the dog's 6th sense?

    August 18, 2011 at 17:24 | Report abuse | Reply
  9. USN, SS RET

    If there is something the dog can smell, we should be able to figure it out and develop a test for it.

    August 18, 2011 at 17:26 | Report abuse | Reply
  10. Sahari

    After a blood transfusion in the hospital, my beloved dog was Verrrrry confused when I came home. Her eyes and ears told her one thing, but her nose was telling her about someone else! It took a while before she became comfortable with me again...

    August 18, 2011 at 18:13 | Report abuse | Reply
  11. doc

    Dint they use one of those smell-sensing devices in Case Antony's case?

    August 18, 2011 at 18:26 | Report abuse | Reply
  12. G. R.R.

    WHile the dog can not say exactly what excites it, there is a way to find out what it is. Try go obtain different scents that will show cancer to a dog and once you do, work to capture and then start splitting it via gas chromatography. From there, you can decide how big it is, etc.

    August 18, 2011 at 18:32 | Report abuse | Reply
  13. alondra

    hi i'm alondra and i am doing a cnn news for my school and i wanted to kno if the dogs will get cancer two

    August 18, 2011 at 19:58 | Report abuse | Reply
    • Heather

      Yes, dogs can get cancer too. Do you think the dog or another dog in the house would smell it and know something was wrong?

      August 19, 2011 at 08:10 | Report abuse |
    • Donna


      I have several dogs that I am handling in the canine ovarian cancer detection study being done at the University of Arkansas for Medical Sciences under a brilliant [and very innovative] physician. You asked if the dogs can get cancer from smelling the scent objects we give them. They can't. Cancer is not contagious. The dogs that are participating in this research are also very carefully monitored by veterinarians who can attest to their health...not because they have any risk of becoming ill from their work, but because we want to be sure that they never have any health issue that could compromise their sense of smell or make them not feel up to working. These are very spoiled dogs that live with their handlers as cherished family members, so we are very attuned to everything that might have an effect on them. As a fun fact, I will add that my dogs were originally rescued from shelters, also work as Search and Rescue dogs and prefer bites of lobster as rewards when they do cancer detection work. Several of the other dogs prefer chicken liver! One of the dogs in our study is deaf. Her name is Lula the Catahoula. As a side study, we hope to determine if a deaf dog has a sense of smell that is heightened to accomodate the loss of hearing.

      August 19, 2011 at 09:26 | Report abuse |
    • Jarno

      Donna – thanks for that post; sounds like very interesting research!

      Though I'd like to correct you on one thing – there do exist a few cancers in the animal kingdom that are contageous. For example, a cancer known as "devil facial tumour disease" has been decimating populations of Tasmanian devils, and it is actually a form of cancer that acts like a parasite, and it spreads through an infected tasmanian devil biting the face of another tasmanian devi, or through an infected tasmanian devil feeding on the same material as other tasmanian devils, or in aggressive mating.

      In dogs, there is actually one transmissible cancer, the Canine transmissible venereal tumor.

      But you are correct, of course, that there isn't any cross species transmission of cancers, and only a few known transmissible cancers altogether.

      August 20, 2011 at 04:16 | Report abuse |
  14. Lynn

    I can smell cancer on people too. It's called cigarette smoke. If you smell like an ashtray chances are eventually you will have cancer. My Grandmother died of bladder cancer at the age of 82. Her doctors said it was caused by smoking. She stopped smoking at the age of 55, but it didn't save her from the damage that was already done to her body. Her Grandmother lived to be 91 so I think my Grandmother lost at least a decade of her life due to smoking.

    August 19, 2011 at 00:58 | Report abuse | Reply
  15. larry

    One breed that has been overlooked is the Tibetan Mastiff. They are very good at this kind of stuff but are not friendly outside what they consider their family unit. They are loyal watch dogs, very intelligent and curious. They are a dog that needs something to do but do not do well in an unstable family environment. Our TM followed with curiosity a training class at a local park. When the trainer noticed that Teddy kept inserting himself into the sessions he tried him out. After being introduced to the samples over a period of several weeks Teddy when tested walked past the ladies lined up, walked up to a lady standing at the edge of the group and barked at her. The trainer said he guessed that Teddy lost interest. We found out from the family that the lady tested positive with no previous history or current symptoms but we were told that TM's would be too difficult to handle and after all the current system was well on it's way to becoming a recognized testing method.

    August 19, 2011 at 09:53 | Report abuse | Reply
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    January 26, 2012 at 04:26 | Report abuse | Reply
  21. Crystal

    I believe that dogs can smell out cancer! We had 2 dogs, my older 13 1 had been in a lot of pain. Later on, he grew a lump on his rear. My 2 year old pup whined every time he smelled it. During an operation, Th vet found that the lump had been cancerous, and most likely of his skin tags had been cancerous too.

    February 25, 2012 at 20:05 | Report abuse | Reply
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      What a horror story; which hnpepas all too often, I'm afraid. I can fully understand your frustrations, and I'm sure you are already aware of all the things you did wrong with the buying of this puppy.However, it is unfair to call you names as some have done or berate you for being a hoarder ; which we do not know to be true. You sound like someone that truly loves animals and care deeply about them. I can also understand you wanting a dream dog , and paying money for her. Although we never did this for any other dog, we paid money for our present furbaby and she's worth every penny of it and then some, even though she is a shih tzu/terrier mix. The only thing I fail to see is why the need for another dog when you already have 7. But, that is your business. In the home where my daughter lives they have 6 dogs, (none of which are pedigree dogs!) and all are well cared for, taken to vets on time, and to groomers all the time; and no, they are not hoarders! They just love dogs.So now, I would like to offer these suggestions: Mix the Merrick canned food with some Merrick dry food, and gradually decrease the canned foods until you are happy with her eating habits) I must say, we feed our little one Merrick dry food, and they are a little more expensive, but she loves them and they are so good and healthy for herAs for her crying when you are gone, I hope your husband will have more patience with her and perhaps even hold her and give her some attention when you are not there, to help her get over her separation anxieties.You didn't say how old the puppy is supposed' to be, and maybe therein lies part of your problem it is just too young to have been taken from it's Mom. And perhaps all the other dogs seem overwhelming and scary to the little puppy. Maybe you need to isolate her while you are gone; and even have her in a crate, and she will soon learn you are coming back and she is safe from all the big guys' out there.Consult with your vet, and see what he/she suggests, and then, all I can say is Good luck dear and God bless.

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Get a behind-the-scenes look at the latest stories from CNN Chief Medical Correspondent, Dr. Sanjay Gupta, Senior Medical Correspondent Elizabeth Cohen and the CNN Medical Unit producers. They'll share news and views on health and medical trends - info that will help you take better care of yourself and the people you love.