Here's an article in Todays Chicago Tribune that says that kosher
food eating has increased to 4 times the level of 1996. They didn't
directly talk about food allergies being a reason to eat kosher, but
it talked about new restaurants, even a Dunkin' donuts (most likely
dairy- only, tho')  [hmm, wonder if they also keep passover- that
would be interesting]

http://www.chicagotribune.com/business/chi-0307220197jul22,1,6910890.story?coll=chi-business-hed
Kosher's not just for the deli anymore

By Rachel Osterman
Tribune staff reporter

July 22, 2003

Dim sum. Thai spring rolls. Even enchiladas.

These days, they all can be purchased kosher. And last week, a
Dunkin' Donuts branch in Skokie obtained certification, the second in
the Chicago area.

Throughout the region, kosher food has surged in popularity. Two
decades ago, few chefs other than those serving deli and Middle
Eastern fare abided by the Jewish laws of kashrut. But these days,
the area has more than 30 certified kosher restaurants.

For food to be classified as kosher, it has to be prepared under a
strict set of guidelines outlined in the Old Testament. Above all,
meat cannot be mixed with dairy, pork and shellfish are not allowed,
animals must be slaughtered in the most humane way possible, and a
rabbi must oversee the whole process.

In recent months, two new establishments--one Yemenite and the other
Moroccan--received kosher approval.
[see web link for rest of the article]