so far from what i've read, only milk causes lactose intolerance...the sugar in milk (lactose) becomes a problem when your body slowly stops producing lactate if i remember correctly...and in most cases happens in adulthood...

symotoms were gas, bloating, ab pain, nausia, squirts...to test, drink some milk...symptoms happen rather quickly, at least for me...i switched to lactose free milk (which tastes better than lactose milk, its sweeter) and my problems went away...but i still had some of my regular milk leftover so i mixed in a tad...symptoms came back...

oh, the gas, from lactose intolerance, AWFUL!...if you have a roadtrip planned with some pals and you have probs digesting regular milk, bring some along