Saliva is a secretion of the salivary glands in the mouth.There is no need to spit it. Tell him to swallow it.
No need for econorm
medicine.Some diseases like liver
problem ,acid reflux
in stomach,etc and also some drugs can cause this salivtion problem.
Hope his liver function tests are OK
For psychogenic cause,convince him that he is OK,give him confidence.
All the best