> So, does that mean that *positive* results can also be false?

Skin tests, yes. I'm not so sure about RAST tests.

>I'm asking  because my son was positive on his RAST test for almost
>everything he was tested for, including foods that I could see no reaction
>from.  So we've just been rotating his diet (within the lower scoring
>foods) so he doesn't get too much of any one food.

Seems like a good strategy, especially for those foods with low positive
values.
>
>He tested positive to lobster, something he had never eaten.  We wondered
>about that.
>
Could he have been exposed in-utero?

Our son hast tested positive (skin tests) to all nuts, but has never eaten
them. The allergist suggests that his skin might be highly reactive (as is
evidenced by his eczema) and that he may be able to tolerate nuts. But he's
also highly atopic, so an oral challenge to these foods (and also
shellfish) is a frightening prospect, and one we would not pursue except as
an in-patient with an IV inserted. Even then, we would do it *very*
carefully, since some reactions cannot be stopped. We've basically decided
to forego any of these challenges, since he's very good about wht he eats,
and since we don't feel like his diet is lacking. Still, we wonder.

Mark