This is just a random thought not based on science lol.... but I have been reading more and more about how animals, especially dogs, seem to be able to detect illnesses in humans faster and more accurately than even our best scientific tests can. What's the big surprise about all of this? We have known for a very long time that a dog's sense of smell is completely off the scale when compared to human scent capabilities...... but ask any parent what they notice about their own children when they are sick and quite often it will come up that 'they smell sick'. I have said it myself countless times - my kids' skin even smelled differently. Nothing I can put my finger on, it doesn't smell 'like' anything, it's just that I am around them all the time and notice when something is 'off'. Their breath gives off a sickly sweet strange odor even.... so if humans can notice something strange, even if we already know that the child is sick, why is it a stretch of the imagination that a dog could sense a strange odor long before we do - even something deep inside the body that we could never smell?
I've read a lot of 'studies' that say it's just happenstance. Or that the animals have some sort of ESP. Or that some are psychic - how about just the plain old regular sense of smell and even hearing? Maybe after spending years with an owner, they get used to the sound of their heart and then detect when something strange is going on (skipping beat, tachacardia, high BP, etc). What if they are used to their owner's scent and then it starts to change and this disturbs the animal so they keep trying to let their owner know? What if they are then used to the smell of a body infected with a particular form of cancer and then 'hit on' someone else with the same odor? It seems pretty reasonable to me. I'm not sure why it's still so heavily controversial.
I remember when I was pregnant for the first time and went over to my neighbour's house for coffee. I was not really showing yet, but was probably about 4 months along. Her cat never had anything to do with me before - would just let me pet her and then she would go lay in the sunshine where no one could bother her. But on this particular day, her cat climbled right up on me and laid flat on my belly with her head at the base of my neck. It was hilarious. She refused to get off and gently dug her claws in when I tried to move her. She started purring and kept it up the whole time!! Right away I thought 'wow, she knows I am pregnant'. After that she would not leave me alone any time I went over there - always laying right ON my belly. When the baby came, she was right back to having nothing to do with me lol. Did she smell that I was pregnant? Could she 'hear' the baby or sense extra heat from me? Who knows, but it was pretty plain to me that she wanted to be near that baby belly and no one could change her mind.
I don't know why it would surprise people to learn that dogs (and other animals) can sense health issues with humans. They can hear something rustling in the bush before we can, hear thunder before we do, sense storms, follow scents of people through forests until a burial site is found, find their way home over 1000s of miles -- on Weird Or What the other day, it said that dogs can even smell fingerprints and distinguish between the people who left their prints.... wow. So why not be able to detect cancer or other illnesses in a living breathing hot blooded human being?