I recently stumbled across a website that offers wonderful assistance in addressing food allergy labeling issues, "Eat, Learn, Live (ELL) is a not-for-profit foundation created to raise awareness of food labeling inaccuracies, to provide advocacy in creating safe educational environments, and to provide tools to assist those affected by food allergies and anaphylaxis. Our efforts are on behalf of the more than 12 million Americans and 2.2 million school-aged children who have a food allergy." I signed up for their newsletter and updates, and received this wonderful checklist on what to do if you have an allergic reaction to a purchased food:

ELL Reminds Consumers of Important Steps to Take Following an Allergic Reaction from a Food Product
 
Reporting an allergic reaction that presumably occurred as a result of a mislabeled food product is very important. Several resources are available that track this type of information.
It is also extremely valuable to have the remaining product tested to confirm the presence of a suspected allergen. Findings will assist the FDA in tracking information about negligent manufacturers. It will also provide validation of the contamination for the manufacturer and hopefully result in a positive action.
 
ELL recommends these steps be taken following an allergic reaction to a mislabeled food item:

• Save the remaining product by securing it closed in its original packaging and wrap in plastic wrap or a zip lock baggie. It will be important to secure the embossed or stamped product code for reference. This code will translate to the batch date/plant location. Be sure to keep any perishable product frozen or refrigerated.
• Contact the manufacturer to inform it of the incident and the suspected allergen ingredient. It may request for you to submit a report. Record the date, time and details of the conversation. IMPORTANT. Do NOT deliver or send the product to the manufacturer if requested! Many times consumers are asked to return the product to be tested by the manufacturer and never hear of “results” of “ingredient testing”.
• Contact your local FDA office to file a complaint. Record the date, time and details of your conversation. You will be given a complaint number to document. To report problems, including adverse reactions, related to any food except meat and poultry, contact the district office consumer complaint coordinator for your geographic area. If the problem involves meat or poultry, which are regulated by the U.S. Department of Agriculture, call the USDA hotline at 1-800-535-4555.
• For ingredient analysis, contact the University of Nebraska’s Food Allergy Research & Resource Program (FARRP), the leading independent food allergy testing laboratory in the US. Please note, testing is FREE of charge only when an allergic reaction resulted from a mislabeled food product. FARRP will test the mislabeled food item for suspect allergen ingredients.
  

FAARP
402-472-4484
143 H.C. Filley Hall
University of Nebraska
Lincoln, NE 68583-0919

• Submit an Allergic Reaction Incident report to Eat, Learn, Live (ELL) at http://www.ellfoundation.org/. ELL will disseminate all pertinent information to its members and follow-up with the manufacturer. Your personal information will be held strictly confidential.

Please feel free to contact ELL if you require assistance with this process or if you have any questions regarding these recommended steps.