Almost everyone knows that dogs have been used for many things due to their higher senses of smell and hearing.  If you watch a show like American Justice or sometimes-even COPS, it's not uncommon to see a dog or dogs sniffing for drugs, explosives, criminals, and even missing children.  But dog's noses provide them with yet another way to help mankind.  They can smell the changes of smell in people to warn of disease.  So far they are used to detect epileptic seizures, low blood sugar and heart attacks.  Some think that they may be able to detect types of cancer in an early stage.

            One theory of how they know says that when our bodies get a disease, our metabolism changes slightly.  This change can affect what smell or chemical we give out.  The change is too subtle for humans to detect but dogs may be able too.  The idea isn't new at all.  Smell has often been used in medicine and still is sometimes today.  One early way of detecting diabetes was by the smell or taste of the patient's urine (I know, gross, but Im not making it up), some burn infections give off a smell, and bad breath can be one of the first signs of gum disease.

            Some others think that dogs notice a small change in behavior and that's why they react.

            Still, even if they do notice something is wrong, how does a trained dog tell their owner something's up?  It varies for different dogs.  Some will go in front of their owner and wouldn't move.  Others will freeze and stare at their owners or push them into a chair.  A few can even call 911 (on a special phone that is.  Imagine dialing your phone with out fingers).