Hi -

I just phoned up my local Bk and asked (explaining about the allergy)
and the manager said:

partially hydrogenated vegetable shortening (soybean), corn solids,
dextrose, dextrin, modified food starch, sodium pyr.... (I couldn't write
fast enough), sodium bicarbonate, xanthum gum and, of course, potatoes.
(There were a couple of other ingredients, not significant to milk
allergy, but I couldn't write fast enough to get them.)

ANy BK should be able to read the ingredients off the package for you.
If you're having a reaction ... I don't know.  The partial hydrogenation?
Or maybe cross-contamination?

Hope this helps.
--Beth Kevles
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  http://web.mit.edu/kevles/www/nomilk.html -- a page for the milk-allergic