hi, u might find this helpful
http://www.babyexpert.com/Baby/Is-your-baby-lactose-intolerant%5E/v1ds is 'cows milk intolerant' (don't know if its the protein or the lactose, or both, but thats how the paeds have all written it on his notes) his started from when he was born although he wasn't officially diagnosed unitl he was 6months, oh and i were both lactose intolerant as babies to, so not a massive surprise. he's one yr old now and he's still precribed sma wysoy (which he's been on since 4.5months), had a follow up with paed a few weeks ago and normally in our case they wld start to test him with cows milk now, which means a day in hospital where the test to see if he's grown out of it or his level of tolerance by starting with 0.5ml and working up til he gets a reaction (not sure what the max is tho)...however ds weight has always been a bit iffy and only now is it on an even keel, so we agreed that we wld wait until he's 2 to do this as i don't want to risk him going down hill again yet, plus he's more likely to have grown out of it by then anyway. however this is to be reviewed in 6 months where they may change their minds then and say to do it then, but we shall see. my understanding is that intolerances can be short term ( a few weeks), long term (a yr or so) or permanent, luck of the draw really. how old is ur lo? if he's fairly newborn i wld imagin its going to be a longterm thing, but if he's older 6m+ then i wld hazard a guess that it will be temprorary but how temprorary there is no way to tell i'm afraid.