Ig E Food Allergy is an Immediate Food Reaction that most people are familiar with. As the name implies, this food reaction can occur within minutes or up to 3 hours after ingestion. Peanuts that cause anaphylaxis in a child is an Ig E food allergy. The reaction is caused by the presence of a high Ig E antibody levels in the blood, which sets off an immediate allergic response. Ig E antibodies make up only a small percentage of our immune system (about 5-10% of our white blood cells), but exert the most severe and life threatening reactions. Symptoms can include rashes or full body hives after eating an apple, immediate vomiting or diarrhea from milk, or an intense headache after drinking wine. These reactions can be tested for by either an allergist or a naturopathic doctor.