France is generally not known for catering to most dietary restrictions, except in larger cities.
You won't find many restaurants with special dishes listed for example.
But you can tell your waiter that you can't have a certain ingredient, for example wheat or walnuts.
I had a client with dairy and gluten issues once, which more or less eliminates 95% of all food in most restaurants, but we found something.
I've also done the same thing with vegetarians and people with nut allergies.
For anyone else reading this, being vegetarian will also limit you to about 5% of the menu in most restaurants.
Your only other options are to not eat French and Alsatian food which personally is a real shame. Of course keep in mind that I'm a foodie. Food and wine are my life ; )