Almost any problem in the mouth, from dental decay to ulcers to tonsillitis can increase the amount of saliva produced. Another big stimulus to saliva production is our brains. We only have to think about or smell food to get the juices flowing. Other psychological factors which affect our brain, from anxiety to excitement, can alter the flow of saliva.

Excessive saliva not necessarily a problem

However, increased saliva production is usually temporary and rarely causes difficulties. We make and swallow up to two litres of saliva every day, but barely notice its passing! Making more saliva doesn't make much difference unless there are problems swallowing it.

If you can't swallow saliva very easily, because of a sore throat or mechanical problems, such as in cerebral palsy or Parkinson's disease (both relatively rare), you end up drooling. This is embarrassing, messy and can make the skin around your lips and mouth sore because it contains the digestive enzyme amylase.

But I suspect that you have a different problem. You may simply have very powerful reflexes in your salivary ducts which squirt out a normal amount of saliva in a large jet from one of the several salivary glands around the inside of the mouth. The opening of one of these ducts may simply be pointing out of your mouth.

Occasionally a small stone may block or partially block one of the salivary ducts, which can cause a backlog of pressure and increased force behind the contractions to eject the saliva.

Drug treatment may have side effects

Some treatments, which include the drug atropine, can be used to reduce the flow of saliva. Although these may help in extreme drooling, they aren't very effective and have undesirable side effects which may get in the way of the saliva's important functions.

Saliva plays an important part in tasting food, digesting it and cleaning the mouth afterwards. It helps to lubricate the mouth for speech, keep the teeth strong and healthy, and is an important defence against bacteria and other infections. When the flow of saliva dries up, as it does in several conditions including some of the changes of ageing, these normal functions can be severely disrupted.

Simpler solutions may be better. First get your dentist or doctor to check your mouth for any cause of excess saliva production, or a stone in the ducts. Then you may need to change your eating habits a little. Try not to talk and eat at the same time (just what our parents always taught us!) and try to talk without opening your mouth too wide or lifting your tongue (some of the largest salivary ducts open under the tongue).

This article was last medically reviewed by Dr Trisha Macnair in July 2008