A study has suggested that dogs can detect cancers in humans.

Using dogs to support the detection and diagnosis of cancer brings significant benefits for humans as it is a low-risk, noninvasive method.

Like many other diseases, cancers leave specific traces or odour signatures in humans.

Cancer cells, or healthy cells affected by cancer, produce and release these odour signatures. They detect these odours in substances called volatile organic compounds (VOCs).

Can dogs smell cancer in humans?

Depending on the type of cancer, dogs can detect VOCs in a person’s:

  • skin
  • breath
  • urine
  • feces
  • sweat

According to Medical News Today, dogs can detect these odour signatures and, with training, alert people to their presence. People refer to dogs that undergo training to detect certain diseases as medical detection dogs.

Trained dogs can 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.

Studies over the past decade have shown trained dogs could identify the urine of patients with bladder cancer almost three times more often than would be expected by chance alone, detect lung cancer in exhaled breath samples with very high accuracy (in two separate studies) and identify ovarian and colorectal cancers by smelling breath samples. 

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Which types of cancer can a dog smell?

Research has shown that dogs can detect many types of cancer, such as:

  • melanoma
  • colorectal cancer
  • lung cancer
  • ovarian cancer
  • prostate cancer
  • breast cancer

For example, one case report 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.