A human can not get any friend more faithful than a DOG. They have been bread since ages to make them more friendly and more useful to humans.
DOGS are well known for their capabilities of extra-ordinary smell. Their property of smelling have been used in various ways by the humans since long time. This has been used for fetching, security and threat detection purposes.
But did you know?
Not only can dogs smell what is present at a distance but can also smell what is present inside our body!!

DOGS can DETECT DISEASES in our body!! Sometimes even before they occur!!
Over course of this friendly relation with our canine friends, we have discovered that dogs react differently when their owners are about to have a disease attack.

Interesting, isn’t it !!

Cancers that can be detected by Dogs-

  • lung cancer (early and late stage)
  • breast cancers (early and late stage)
  • prostate cancer from urine samples
  • bladder cancer from urine samples
  • colo rectal cancer from stool samples
    • melanoma (skin cancer)
    • ovarian cancer


    When a human is sick or suffering from a disease, the diseased cells undergo some abnormal reactions. The byproducts produced in these abnormal reactions are secreted in sweat, urine or stool or exhaled in breath by humans.

    These are called as VOLATILE compounds.

    Since dogs have an amazing capacity of smell, they detect these volatile substances.

    Some examples of the diseases are-

    STOOL – infectious bowel diseases such as Clostridium difficile, Campylobacter, Salmonella and Cholera.irritable bowel syndrome and inflammatory bowel disease

    URINE -urinary tract infections, bladder, prostate and other cancers. 

    BREATH – lung cancer (Alkanes and monomethylated alkanes)


    Dogs have been able to detect other important complications such as HYPOGLYCEMIA, SEIZURES even before onset of their symptoms. The exact reason of this is still unknown. But this has helped owners to save their lives. 


    These changes in biogenic volatile organic compound concentrations can be used to mirror pathological processes in the whole body or blood concentrations of drugs (e.g. propofol) in clinical settings—even during artificial ventilation or during surgery.

    Noninvasive detection and therapeutic monitoring of oxidative stress would be highly desirable in autoimmunological, neurological, inflammatory diseases and cancer, but also during surgery and in intensive care units. 


    LUNG CANCER- sensitivity of canine scent detection compared to biopsy-confirmed conventional diagnosis ranged from 71% to 99% and overall specificity 93% to 99%. Lung cancer detection was independent from COPD and the presence of tobacco smoke and food odours.

    BREAST CANCER- sensitivity was 88% and specificity 98%

    BLADER CANCER- sensitivity ranged from 64% to73% and specificiy 56% to 92%


    Acoording to questionare based study, when the dog owners were asked how many times have the dog helped them in detecting their hypoglycemic incidences, the results were highly supportive-

    65.1% respondents indicated that their dog had shown a behavioral reaction to at least one of their hypoglycemic episodes. 36% believed that their dogs reacted most of the times they went “low”; 33.6% indicated that their pets reacted before they themselves were aware they were hypoglycemic.

    COLO RECTAL CANCER-  The sensitivity of canine scent detection of breath samples compared with conventional diagnosis by colonoscopy was 91% to 97% and the specificity was 99%. The accuracy of canine scent detection was high even for early cancer.

    MELANOMA- In an accidental finding, a dog detected the presence of cancer cells on skin much before it became a symptom. The patient had no symptom or spots on skin but thorough histopathological examination in this individual then confirmed melanoma in a fraction of the cells.

    OVARIAN CANCER –  Double-blind tests showed 100% sensitivity and 97.5% specificity. Moreover, the odor of ovarian carcinomas seems to differ from those of other gynecological malignances such cervical, endometrial, and vulvar carcinomas.

    SEIZURES- Findings suggest some dogs have innate ability to alert and/or respond to seizures. Suggests a trend in type of seizure/auras a dog may alert to. Success of these dogs depends largely on the handler’s awareness and response to the dog’s alerting behavior. 

    PROSTATE CANCER- The sensitivity 98%-100% and specificity were both 91%- 98%.

    Dogs also showed high sensitivity and moderate specificity for detecting urinary tract infections in comparison to culture, especially for Escherichia coli. 

    MALARIA- Dog distinguished between sock samples from malaria-infected and uninfected school children, with a sensitivity of 70% to73% and specificity of 90% to 91%.

    All of these suggest that the results obtained from using dogs as detection tool for diseases might be variable in various diseases but are definitely more than a luck by chance findings (14%).


    Dogs, just like how they are trained for other activites, are trained to detect the specific smell from known patients using rewards methodology. This is similar to how canines are trained to detect drugs and explosives.

    A video by CAMBRIDGE UNIVERSITY explains this process how dogs are trained to detect hypoglycemia.

    Ordinary household dogs with only basic behavioral “puppy training” can be  trained to accurately distinguish breath samples of lung and breast cancer patients from those of controls, in a matter of weeks.

    To properly train a dog it may take, 6-8 weeks for a dog that is already trained to detect other scents or 3-6 months for a dog that has never been trained.


    Various forms of reactions have been noted by various sniffer dogs owners. It can range from vocalizing (61.5%), licking them (49.2%), nuzzling them (40.6%), jumping on top of them (30.4%), and/or staring intently at their faces (41.3%). 

    A smaller proportion showed behavioral responses suggestive of fear, including trembling (7.2%), running away from the owner (5.1%), and/or hyperventilating (2.2%).

    It has been seen in some patient’s interview that, these reactions changed as the bond between the owner and pet strengthened over time.


    The sex, age, breed status, and length of pet ownership were found to be  unrelated to response likelihood of disease detection.

    This is non invasive, portable method requiring no laboratory set-up for disease detection.


    Dogs in some prospectes resemble humans to some or other extent. Just like humans they suffer from mood swings, depression, health issues and react according to their surrounding, up bringing and bond with their owners.

    They are subject to boredom, fatigue, and an incentive to gain reward for minimum effort much like the humans they work with. 

    Hence, researchers, trainers, and practitioners of canine-based diagnostics should recognize these personality aspects of dogs and develop specific controls and guidelines to assure that the dogs are working to the best of their olfaction abilities.

    Some people tend have fear of dogs. This will obviously come in the way when direct contact comes into picture.

    Also dogs also require to be looked after, trained and regularly check for health issues. All of this is a time and weath consuming process.


    There have been some organisations working towards this novel cause. These are experts in training dogs and providing them to patients who require such dogs to save their lives.

    MEDICAL DETECTION DOGS has been working on this and providing people with trained sniffer dogs who can help the paients from life threatning incidences.

    The site contains patient’s interviews indicating how trianed sniffer dogs have saved their lifes by alerting about diseases such as- anaphylaxis, hypoglycemia, epileptic disorders, postural orthostatic tachycrdia syndrome, addison disease, 

    ASSISTANCE DOGS INTERNATIONAL has been working through its various centres around the globe in trainein gand providing the patients such trianed sniffer dogs.


    Well, not much research on this topic has been done so far, but it is assumed by expert that just like other diseases, corona patients also expel certain volatile compounds in the breath which can be detected by strong nose of a dog.

    Few studies conducted also support this theory. In a sudy, it was found that dogs were able to discriminate between samples of infected and non-infected individuals with average diagnostic sensitivity of 82.63% and specificity of 96.35%. The dogs achieved an overall average detection rate of 94%.

    Points to keep in mind while using a MASK-



    Canine olfaction could become a preferred methodology for disease diagnosis in emergency situations (infection epidemics) and in places where high-tech instrument-based analysis is unavailable. Also these can be deplyed at locations requiring vast screening such as air-ports, railways and similar.

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    1. Canine olfaction as an alternative to analytical instruments for disease diagnosis: understanding ‘dog personality’ to achieve reproducible results by Klaus Hackner and Joachim Pleil; Published 9 January 2017 • © 2017 IOP Publishing Ltd;Journal of Breath Research, Volume 11, Number 1
    2. The human volatilome: volatile organic compounds (VOCs) in exhaled breath, skin emanations, urine, feces and saliva by Anton Amann and others
    3. Diagnostic Accuracy of Canine Scent Detection in Early- and Late-Stage Lung and Breast Cancers by Michael McCulloch, and others
    4. Detection of Lung Cancer With Volatile Markers in the Breath by PhillipsMichael and others
    5. Volatile organic compounds as biomarkers of bladder cancer: Sensitivity and specificity using trained sniffer dogs by Carolyn M Willis and others
    6. Olfactory detection of human bladder cancer by dogs: proof of principle study by Carolyn M Willis and others
    7. Canine responses to hypoglycemia in patients with type 1 diabetes by Deborah L Wells 1, Shaun W Lawson, A Niroshan Siriwardena
    8. Colorectal cancer screening with odour material by canine scent detection by Hideto Sonoda and others
    9. Evidence for canine olfactory detection of melanoma by DuanePickel and others
    10. Seizure response dogs: evaluation of a formal training program by A Kirton and others
    11. Human ovarian carcinomas detected by specific odor by György Horvath and others
    12. Seizure-alert dogs: a review and preliminary study by Deborah J Dalziel and others
    13. Olfactory detection of prostate cancer by dogs sniffing urine: a step forward in early diagnosis by Jean-Nicolas Cornu and others
    14. Sniffing animals as a diagnostic tool in infectious diseases by E.Cambau12M.Poljak
    15. medicaldetectiondogs.org.uk
    16. https://assistancedogsinternational.org/
    17. Trained dogs identify people with malaria parasites by their odour by Claire Guest and others
    18. An Owner-Independent Investigation of Diabetes Alert Dog Performance by Clara Wilson and others
    19. Olfactory system of highly trained dogs detects prostate cancer in urine samples. byGianluigi Taverna and others
    20. Scent dog identification of samples from COVID-19 patients – a pilot study by Paula Jendrny, and others

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