Hi, The safest approach for a project like this is most likely a research or demonstration project (rather than an experiment).
http://chemistry.about.com/od/sciencefairprojects/tp/typesciproject.htm

The website of the American Academy of Allergy, Asthma & Immunology has suggestions and information to help you and your daughter complete the project you seek to do:

http://www.aaaai.org/patients/just4kids/science/humanbody.asp
http://www.aaaai.org/patients/publicedmat/tips/foodallergy.stm

You can also find helpful information on these pages of Education.com:

http://www.education.com/reference/article/Ref_Organizing/
http://www.education.com/topic/help-child-with-science-fair-projects/

I also suggest that you talk to your child's teacher to gather information about any guidelines or parameters the teacher or school has set for the science fair.