Welcome to healthcare Magic!
is a life threatening phenomenon, you should remember the name of the painkiller and avoid it in future.
The dry mouth
may be related to stress of surgery or the remnant allergic reaction
You should take frequently the house hold liquid diets like warm soups/tea etc. Lemon water would also be good.
I would advise to continue tablet levocetirizine
5mg for 5 days to come.
I hope the advise would be informative and useful for you.