I would like to add that as there are different types of p then there are different causes of the condition.
Majority of people who i know with p have problems with there stomachs and backs therefor giving evidence to a digestive problem. They are suffering from flakey type (sry forget the name)
I have done alergy tests and been told to stay away from wheat and dairy and also sugar ie in cakes ets, which is near impossable.
When something breaks out in your skin its always an internal problem, this is common sence.