The Superpower of a Dog’s Nose

A dog’s nose is extraordinary — it contains up to 300 million olfactory receptors, compared to about 5–6 million in humans. Their sense of smell is estimated to be 10,000–100,000 times stronger than ours. This ability allows them to pick up volatile organic compounds (VOCs), which are chemical markers of disease that the human body releases through breath, sweat, or urine.

Scientific Studies on Dogs Detecting Illness

Over the past two decades, multiple studies have confirmed dogs’ ability to detect illness. For example:

• A 2004 study published in the British Medical Journal found trained dogs could detect bladder cancer in urine samples with 41% accuracy — significantly higher than chance.
• A 2011 German study showed dogs were able to detect lung cancer in breath samples with 71% sensitivity and 93% specificity.
• More recently, in 2020, dogs trained in the UK were able to detect COVID-19 with up to 94% accuracy in laboratory conditions.

These findings highlight that canine scent detection isn’t just anecdotal — it’s being tested and used in medical research worldwide.

Types of Illnesses Dogs Can Detect

Dogs have been trained (and sometimes naturally notice) to detect a range of human illnesses, including:

• Cancer – including breast, bladder, lung, prostate, and skin cancers.
• Diabetes – detecting dangerous drops in blood sugar (hypoglycemia).
• Seizures – some dogs alert their owners before an epileptic seizure.
• Infections – identifying bacterial infections such as Clostridium difficile.
• Viruses – including COVID-19 and potentially influenza strains.

Real-World Examples of Detection

There are countless stories of dogs saving lives by detecting illness early. One case involved a woman whose Labrador persistently nudged at a mole on her leg — later diagnosed as melanoma. Another involved diabetic alert dogs, trained to alert owners before blood sugar reached dangerous levels, sometimes up to 20 minutes in advance.

How Dogs Actually Detect Illness

Dogs don’t consciously “diagnose.” Instead, they pick up on scent changes caused by illness. VOCs released by tumors or infections create a smell signature that dogs can detect at incredibly low concentrations — sometimes parts per trillion. They may also notice subtle changes in behaviour, body temperature, or energy levels in their humans.

Everyday Signs Your Dog Senses Something

Even without formal training, your dog may pick up on changes in your health. Signs include:

• Unusual sniffing or licking of a specific area of your body.
• Sudden clinginess or protective behaviour.
• Alerting or whining when something seems wrong.
• Restlessness or pawing if you’re unwell.

If your dog consistently focuses on one area of your body, it may be worth getting it checked by a healthcare professional.

FAQs

Can all dogs detect illness?

While all dogs have powerful noses, not every dog will show interest in detecting illness. However, with training, many can develop reliable detection skills.

Which breeds are best at illness detection?

Labradors, German Shepherds, and Spaniels are often used in scent detection due to their keen noses, trainability, and motivation to work. That said, almost any breed could be capable.

Should I rely on my dog for medical advice?

No — dogs can be incredible at picking up illness, but they’re not a replacement for medical professionals. If your dog persistently focuses on a certain behaviour or area, it’s best to see a doctor.