Drooling (or sialorrhea) is common in PD.
For the most part the cause is not increased saliva production but slowed reflex in automatically swallowing the natural saliva that accumulated in the mouth throughout the day.You see, a person without PD does not even notice that saliva is constantly being produced (it is done so to lubricate the whole mouth for talking, eating)
This is because after a certain volume is accumulated, this is automatically swallowed without even thinking about it.
But in PD, this automatic swallowing is sometimes lost, thus the saliva pools and drools on the side of the mouth.
I have experience saliva drooling due to poor automatic swallowing of my throat as the result I feel uncomfortable.
I some times lost appetite and difficulty to swallow either to eat or drink as the saliva is constantly being produced. I have a feeling that food or liquid is sticking in the throat during or after a meal. As the result I have coughing or choking