Humans have put dogs' remarkable sense of smell to use by training them to sniff out explosives and narcotics. Their powerful noses can also detect viruses, bacteria, and signs of cancer in a person's body or bodily fluids.
In this article, we look at the evidence behind dogs' abilities to smell and identify different types of cancer, and how medical professionals can use dogs to help diagnose the condition.
Can dogs smell cancer?
Dogs can detect cancer odor signatures in a person's skin, urine, and sweat.
Research suggests that dogs can detect many types of cancers in humans.
Like many other diseases, cancers leave specific traces, or odor signatures, in a person's body and bodily secretions. Cancer cells, or healthy cells affected by cancer, produce and release these odor signatures. Depending on the type of cancer, dogs are able to detect these signatures in a person's:
Dogs can detect these odor signatures and, with training, alert people to their presence. People refer to dogs that undergo training to detect certain diseases as medical detection dogs.
They detect some substances in very low concentrations, as low as parts per trillion, which makes their noses sensitive enough to detect cancer markers in a person's breath, urine, and blood.
Which types of cancer can a dog smell?
Research has shown that dogs can detect many types of cancer. For example, a case study published in BMJ Case Reports describes how a 75-year-old man visited a doctor after his dog licked persistently at a lesion behind the man's ear.
The doctor performed diagnostic tests and confirmed malignant melanoma.
While nobody had trained this person's dog to specifically detect cancer, most research studies into canine cancer detection involve teaching individual dogs to sniff out specific cancers. Trained dogs are able to detect colorectal cancer from people's breath and watery stool with high levels of accuracy, even for early stage cancers. The presence of gut inflammation or noncancerous colorectal disease does not seem to affect dogs' ability to detect these cancers.
Dogs can also detect lung cancer from a person's breath. One study found that a trained dog had a very high rate of accuracy in distinguishing between the breath of people with and without lung cancer.
They are also able to detect ovarian cancer from blood samples and prostate cancer from sniffing a person's urine.
One study found that dogs trained only to detect breast cancer were also able to detect melanoma and lung cancer, meaning that there may be a common odor signature across different types of cancer. Are dogs used in cancer research and diagnosis?
Diagnosing cancer with dogs is low-risk and noninvasive.
The fact that dogs can detect cancer has significant benefits for humans. Using dogs to detect and diagnose cancer is a low-risk, noninvasive method. Medical detection dogs present few side effects and may offer advantages because they are mobile, can begin work quickly, and can trace an odor to its source.
They also have the potential for use in patient care settings or laboratories to identify cancer in tissue samples from people with suspected cancers.
Dogs' abilities may also help with developing machines that can reliably detect odor signatures from cancer, such as electronic noses.
However, research is still underway and the effectiveness and reliability of canine cancer detection requires further research.
Dogs have an incredibly sensitive sense of smell that can detect the odor signatures of various types of cancer. Among others, they can detect colon cancer, prostate cancer, breast cancer, and melanoma by sniffing people's skin, bodily fluids, or breath.
Researchers are currently exploring the possibility of using specially trained medical detection dogs in the diagnosis and tracking of cancer.
Canine cancer detection is a simple, noninvasive procedure with potentially fewer side effects for people. However, further investigation is necessary to validate this method for use in clinical practice.