Many dog owners believe their pets have a sixth sense when it comes to detecting health problems in their human companions. Dogs have an incredibly sensitive sense of smell that can detect subtle changes in odor given off by a person’s body when they are unwell. But do dogs really have an innate ability to sense impending death or disease?
Do dogs know when you are sick?
There are numerous anecdotal accounts of dogs appearing to recognize when their owners are unwell before symptoms manifest. Many people report that their dog began acting differently around them in the early stages of an illness, sticking closer than usual and seeming protective or concerned. Some dogs have even been known to sniff or lick at parts of the body later found to be affected by cancer.
Scientific studies have uncovered evidence that dogs can detect some cancers through odor. Research shows trained dogs can detect lung, breast, ovarian, bladder and prostate cancers from odor on the breath or urine at very early stages.[1] Dogs’ noses have around 300 million scent receptors, compared to humans’ measly 5 million, making them extremely sensitive to odors we might not notice.[2]
Dogs are also able to pick up on subtle cues in human behavior and appearance when someone is feeling under the weather. Changes in body language, facial expression, appetite, activity level, and routines can alert dogs that something may be amiss before obvious symptoms appear.
Ways dogs detect illness
- Changes in odor
- Subtle changes in behavior/appearance
- Ability to smell chemical changes
Do dogs detect cancer?
There are many reports of dogs alerting owners to cancers of the skin, breast and bladder. Dogs have even been trained to detect lung and ovarian cancer through breath and urine samples.
One study found trained dogs could detect lung cancer with around 70% accuracy just from sniffing the breath of patients who had already received diagnosis. They could do this even in early stage 1 cancers.[3]
Scientists believe dogs can smell minute chemical differences emitted in the breath and urine of cancer sufferers. Some studies suggest cancer cells release different metabolic waste products than healthy cells.[4]
Cancer types dogs can potentially detect
- Skin cancer
- Breast cancer
- Bladder cancer
- Lung cancer
- Ovarian cancer
While dogs clearly have an enhanced olfactory system allowing them to detect cancer in some circumstances, more research is needed before their diagnostic abilities can be definitively proven.
Can dogs sense seizures and blood sugar changes?
In addition to detecting cancer, some dogs are also trained as seizure alert dogs. These dogs are thought to respond to subtle odor changes that may occur prior to an epileptic episode, alerting their owner so they can get to safety.[5]
Dogs are also used as hypoglycemia alert dogs for people with diabetes. They appear capable of detecting slight variations in blood sugar levels, likely through odor cues on their owner’s breath. They can notify their diabetic handler when their blood sugar gets too low by nudging or making noise.[6]
Conditions dogs can potentially alert to
- Seizures
- Hypoglycemia
While dogs show promise for alerting prior to seizures or blood sugar crises, rigorous studies confirming their accuracy are still needed.
Can dogs sense pregnancy?
Anecdotal reports indicate dogs may detect pregnancy in humans before visible signs appear. Many owners say their dog became more protective, affectionate and clingy in the early stages of pregnancy before they had confirmed they were expecting.[7]
It’s thought dogs use their highly advanced sense of smell to detect subtle hormonal changes and slight variations in their owner’s scent very early on in pregnancy.
Studies have shown trained dogs can detect pregnancy in humans by sniffing blood samples with around 97% accuracy if the blood is drawn in the third trimester.[8] Their ability to detect very early pregnancy is less proven.
Ways dogs may sense pregnancy
- Change in owner’s scent
- Hormonal changes
- Behavioral/physical changes
Do dogs know when you’re sad or stressed?
Dog owners often believe their pets know when they are experiencing emotional distress. Many report their dogs comforting them when sad or stressed.
Studies show dogs can differentiate between human emotional states through visual and auditory cues. Dogs will approach crying people over humming people and can match emotional vocalizations to facial expressions.[9]
Signs of stress dogs may pick up on include:
- Changes in body language/posture
- Altered tone of voice
- Irregular behavior patterns
- Different pheromones
So while dogs lack innate psychic abilities, their powers of perception and emotional intelligence should not be underestimated.
Can dogs sense approaching death?
Many caretakers of elderly or ill individuals report their pet dogs sticking close by and seeming to recognize impending death. This has led to a widespread belief that dogs have a sixth sense about when someone is nearing the end of life.
There are a few theories that could explain dogs’ potential ability to detect approaching death:
- They may smell chemical changes occurring in the body
- They notice behavioral changes in the person
- They pick up on the emotional state of caregivers
While these factors hint dogs might have insight into health changes as the end nears, there is no conclusive scientific evidence they can sense impending death itself.
Signs a dog may detect impending death
- Increased clinginess
- Refusing to leave person’s side
- Altered behavior around individual
Conclusion
In summary, dogs appear to have some ability to detect changes in human physiology and behavior that may relate to ill health, emotional state or pregnancy. Their advanced sense of smell seems key to detecting cancer in some cases and subtle odor changes caused by other conditions.
However, more research is still needed to prove dogs can sense things like pregnancies and impending death. While they have great perceptual abilities, dogs do not have psychic insights into human health. Any abilities they display are likely based on their powers of smell and observation rather than a supernatural sixth sense.
| Condition | Evidence dogs can detect |
|---|---|
| Cancer | Moderate evidence for some cancers based on smell |
| Seizures | Anecdotal, research needed |
| Diabetes | Anecdotal, research needed |
| Pregnancy | Minimal evidence, possible smell cues |
| Emotions | Good evidence through visual/audio cues |
| Impending death | Only anecdotal, no proof |
Dog owners should look out for subtle changes in their pet’s behavior that could indicate a health problem. However, a dog seeming to sense illness is not definitive proof of a medical issue. Key takeaways:
- Dogs have an excellent sense of smell that allows them to detect some diseases
- More research is needed into abilities such as sensing seizures or pregnancy
- Dogs read human behavior/emotions well but cannot foresee death
- Any sensing is likely based on smell/behavior cues rather than a sixth sense