So here is my advice if your child has an unusual food allergy: send a listing of all ingredients that your child cannot consume to the company whose food you want to eat. Then wait for a response.

Then - even if the company gives you a clean bill of health - and only then - have your child eat only a very, very small amount - sort of putting the toe into the water before you throw her all the way in. Make sure you have an epipen handy - just in case. Wait 24 hours and see if your child keels over and dies. If not then you can revisit the restaurant.

This advice applies as well to adults who have known allergies:

Daily News Central, 19 Feb 2006, McDonald's Sued for Failing to Disclose Gluten, Dairy in Fries

McDonald's Corp. faces at least three lawsuits claiming the fast-food giant misled the public after it acknowledged earlier this week its french fries contain milk and wheat ingredients.

Debra Moffatt of Lombard, Ill., seeks unspecified damages in a suit filed last February in Chicago. Her attorney, Thomas Pakenas, said his client has celiac disease, which causes gastrointestinal symptoms set off by eating gluten, a protein found in wheat.

...

Before its acknowledgment, the company had quietly added "Contains wheat and milk ingredients" to the french fries listing on its Web site.