Peanut Allergy is the most prevalent food allergy in the US, where as many as 1.5 million people suffer from the disease (American Academy of Allergy, Asthma & Immunology). Peanut Allergy is the most common cause of food related death (Asthma and Allergy Foundation of America).
More Statistics...
It's not so much the type of flour that you need to worry about (unless of course it's peanut flour). What you need to worry about is where the flour is made, how it's packaged, and if there are peanuts in the facility.
If you find a particular brand you like you can call the company and ask what their manufacturing processes are.
Hope that helps!
Ruth