You may not know this about my family but there are a lot of food allergies we deal with, obviously on the daily basis. I am constantly trying (and sometimes failing) new recipes with alterations to fit our diet restrictions.
Whether you need substitutions due to a medical condition like an intolerance or allergy or if it is a lifestyle choice this post will be helpful for you. Food allergies can range form just not feeling yourself when you eat something all the way to a life threat. A Food sensitivity is usually catgorized as IgG allergy. The more severe allergy is where there is an IgE reaction that can cause an anaphylaxis resulting in death. Some chose not to eat certain types of food due to their religion or views on life.
One of the 8 main Food allergens are eggs, so here is a good chart for egg substitutions:
Here are a few for flour substitutions from allrecipes: