Wikipedia Entry

Wikipedia gives a very good description of food allergies and the resulting symptoms and side effects.  Because there is no cure for allergies there are often additional complications for the allergy sufferer.  I added a paragraph to Wikipedia highlighting some of the symptoms and side effects allergy sufferers have to deal with when confronting allergies on a daily basis.

Below is the original Wikipedia entry and in block format is my addition.  You can view it on Wikipedia at  https://en.wikipedia.org/wiki/Foodallergy.

A food allergy is an adverse immune response to a food protein.^[1][2][3]

They are distinct from other adverse responses to food, such as food intolerance, pharmacological reactions, and toxin-mediated reactions.^[4]

The protein in the food is the most common allergic component. These kinds of allergies occur when the body's immune system mistakenly identifies a protein as harmful. Some proteins or fragments of proteins are resistant to digestion and those that are not broken down in the digestive process are tagged by the Immunoglobulin E (IgE). These tags fool the immune system into thinking that the protein is an invader. The immune system, thinking the organism (the individual) is under attack, sends white blood cells to attack, and that triggers an allergic reaction. These reactions can range from mild to severe. Allergic responses include dermatitis, gastrointestinal and respiratory distress, including such life-threatening anaphylactic responses as biphasic anaphylaxis and vasodilation; these require immediate emergency intervention. Individuals with protein allergies commonly avoid contact with the problematic protein. Some medications may prevent, minimize or treat protein allergy reactions. There is no cure. 

Complications from allergies can be frightening.  It is important to be conscious of what you are eating at all times because once you have an allergic reaction you will need to go through a recovery process to feel better.  With anaphylaxis that process could take days as most emergency rooms administer steroids to minimize the reaction.  With less violent reactions you will still not feel well for a few days.  During that time your immune system is compromised and more susceptible to other infections and illnesses.  I added the following to Wikipedia.

Allergies, however, do result in a weakened immune system making the allergy sufferer more susceptible to other infections and viruses.  Allergy reactions tax the immune system resulting in becoming more sensitive to other allergens, becoming more sensitive to pain and easily catching whatever cold or flu is currently running its course.  The best way to avoid additional symptoms and a weakened immune system is to avoid all contact with allergens including food sensitivities.