Horrible nappies after eating yogurt???? Possibly

[IneedacleanerIamalazyslattern]

DS (3) has never drunk milk. He had reflux when he was born for about a year and when he stopped bf at about 18 months he wouldn't drink milk at all and never has he won't even try it now just adamant he doesn't like it.
He is a pretty fussy eater on the whole and wouldn't eat yogurts either until recently (past month) around this time he started getting rally bad diarrhoea accompanied by a really really sore bum.
Now I did mildly speculate at the time that it started that it may be the yogurts then it stopped.
Now I bought yougurts the other day for the first time in a while (they usually end up sitting in the fridge going off) ds has horrible diarrhoea again and a sore bum.

Is it the yougurts, is it some kind of allergy/inotlerance is it dairy??
It doesn't take much for his stools to soften (bit too much fruit, oranges/juice) but never to this extent it is running down his legs when it happens.
He doesn't eat anything actually that I can think of that is directly dairy, he does obviously eat things with dairy products in them but doesn't eat cheese etc.

Should I take him to the doctor do you think?
SOrry this is long i'm partly trying to track all this events in my own head and figure out if it could be anything else but it really can't.

[blondissimo]

I'd say it's probably a dairy intolerance - either lactose or cow's milk protein - not sure how you distinguish which. I would take him to the gp and just explain things and see what they say - there is not a lot they can do but they might be able to give you advice.