But human saliva is much more important than many people realise, University of Otago researcher Dr Sara Hanning says.
And insufficient saliva - linked with xerostomia, the subjective feeling of having a dry mouth - is a significant health problem for many older people.
It can cause ''massive'' dental decay if the ''buffering'' effect of saliva is lost, in countering the acidic nature of certain foods and drinks, she warns.
Some people with excessively dry mouths also have trouble eating and talking, and find it hard to taste food and drink.
Such problems were ''underestimated'' and most people with ''normal saliva'' did not think about it, she said.
But as New Zealand's population aged, many more people were affected - and hundreds of thousands of people, many of them over the age of 65 - already had the condition.
An autoimmune syndrome, as well as many metabolic, respiratory and neurological diseases contributed, and some medications also cause or add to the problems.
Dr Hanning, who recently graduated with an Otago University PhD in pharmacy, has been developing a saliva substitute - which includes water, and an oily substance - to counter dry mouth.
Water alone often quickly drains away, and the dryness persists.
She is keen for her saliva substitute to ''make a difference'' and her hopes may be moving closer to reality.
One of her substitute formulations is likely to be tested in a clinical trial involving about 40 people in Christchurch this year.
Over the years, some of her friends have given her a good-natured ribbing about her slightly unusual interests, but friends and family have also been ''very supportive'' about her research.
During her studies, she visited Queen's University, Belfast, in Northern Ireland, in 2011 where she used a rheometer, a laboratory device which measures the way a liquid flows when forces are applied.
One of her supervisors, Associate Prof Natalie Medlicott, of the Otago School of Pharmacy, said Dr Hanning's research was promising, and was associated with the university's ''formulation and delivery of bioactives'' research theme.
