Hello welcome to ecf, I'll try to offer some information that may be helpful.
Many have this problem, many don't. If you do, it can be really bad in the beginning, very painful I've been there, and then it passes.
Yes many do get it and I myself.. It does pass but can reoccure. The first few times are bad outbreaks. Drinking some water regularly is very helpful for rinsing the juice components off your mouth.
I have two theories.
I haven't quite identified what causes an outbreak but its something. Right now i think that it is nicotine related meaning the brand of nic. There's different processing methods and some leave chemicals that cause the outbreaks. Also could be a flavoring.
It also has to do with the environment change in the mouth from the vapor. Pg drys the membranes, vg super hydrates them.
My environment theory.
Your environment dictates what ratio of Pg/vg will be best. Also the individuals body. In a dry climate you want the vg ratio to be higher to balance the dry air . In a humid climate you want more Pg to balance the humidity.
Too much dry and your throats dry, too much moisture and your too wet.
In Egypt, if its arid, I would go as high vg as you can get. It will take time for the sore outbreak to heal possibly over a week up to two.
Whatever I'm doing now I've been clear for a long time. Vaping 3 years now.
Good luck.