The most severe allergic reaction is anaphylaxis — a life-threatening whole-body Anaphylaxis can come on within minutes of exposure to the trigger food. It can be fatal and must be treated promptly with an injection of epinephrine (adrenaline). Sourced from: http://acaai.org/allergies/types/food-allergy
Allergy reactions vary from person to person. Not all reactions are severe and there are those that are severe to the point of being life threatening.
Studies show organic foods contain higher vitamin C, iron, magnesium and phosphorus are significantly lower in pesticide residues and higher in antioxidant activity. Sourced from: http://www.huffingtonpost.com/dr-susanne-bennett/allergies_b_1363995.html