We could not swallow our food without it, sing or even whistle.  Cats wash with it, and humans swallow up to a litre a day.   It can be antibacterial and mice heal their wounds with it.  Spit, saliva, drool, mucus, whatever you call it, we cannot do without it.

 

Saliva is produced in response to smelling food, and when food in the mouth is being chewed.  Think right now of your favourite food, and within seconds your mouth will be filled with saliva in anticipation.  The chewing of food also stimulates the production of saliva to help us swallow. A dog waiting for his dinner as you slowly open the can of dog food will drool.  Without saliva, we cannot taste our food.   The mucus in saliva is important to bind our food together into a swallowable portion that is slippery enough to slide down the throat and into the stomach.  Saliva coats the lining of the mouth and throat and protects that delicate skin from being torn or damaged by our food.  

 

There are three main glands that produce saliva, the parotid near the ears, one under the tongue and another by your jaw.  There are lots of other smaller glands scattered throughout the mouth, you can feel them as little bumps in the cheek and lips.  One way you do not want to find out exactly where your parotid gland is to catch the mumps.  This is a very painful viral disease of the parotid gland that leaves you very swollen and looking like a hamster cramming on overdrive.

 

Morning bad breath is caused by a slowdown in saliva production when we are sleeping. Without saliva to constantly flush bacteria from the mouth, the numbers build up.  Saliva contains enzymes that kill bacteria by lysing or bursting their cell walls and is at the frontline of the body’s defences containing a powerful cocktail of antimicrobial agents including Immunoglobulin A (IgA). The IgA antibody recognizes and disables breathed in or swallowed bacteria or viruses.

 

We would all have rotten teeth without a healthy dose of spit. ’If saliva were water, we would have little stumps of teeth or no teeth at all by age 20-we would have dissolved our teeth away," says Frank Oppenheim, a dental researcher at Boston University.  After eating, plaque bacteria get to work on leftover bits of food.  Within 10 minutes they produce enough acid to start dissolving the hard white enamel on our teeth.  Saliva saves the day by neutralizing the acids and protecting our teeth.

 

Dutch scientists are testing artificial salivas. They've developed fake salivas containing synthetic gums or mucins harvested from pig stomachs that have a slithery feel in the mouth. ‘ It's tough to create anything close to a fluid that's been fine-tuned through millions of years of evolution,’ says Arie van Nieuw Amerongen of the Academic Center for Dentistry in Amsterdam. ‘Hardly anybody thinks about spit. But when they miss it, they see how many properties it has--and how difficult it is to mimic.’

 

A swab sample of spit taken from the inner cheek is how forensic scientists take a DNA sample.  The saliva contains enough skin cells to analyse and can identify an individual.  They can even get enough of a sample from the saliva used to lick a postage stamp, that is left on the envelope.  After a spate of unpleasant assaults where bus drivers were being spat at by angry passengers, London transport workers were issued with a DNA testing kit. Last year a 17 year old was arrested after being identified from his saliva.