Interesting question.

You could try something that's high in casein and low in lactose. 
That way, if there are GI symptoms, they'd be more likely to be 
allergic in origin rather than due to a lactase deficiency. But 
cheeses might introduce other factors, such as molds.

How about Lactaid milk?

Mark

At 04:45 PM 1/25/2007, you wrote:
>Do we have to challenge diary with milk or can we do it with a milk =
>product like yogurt instead?
>Are there any advantages or disadvantages to that approach?