Two types of food reactions are observed from allergic foods:

  1. Pharmacologic food reactions: also known as false food allergies
  2. Metabolic food reactions: also known as true food allergies

Certain foods contain substances that can be allergic to human beings. The substance present in food binds to receptors present on and in the cell; receptor sensitization results in a series of exaggerated reactions. These reactions occur even if minor quantities of the allergic food is ingested.  These are commonly known as pharmacologic food reactions.

Other type of food reactions are metabolic food reactions. These reactions occur only when excess quantity of an allergic food is eaten. Low quantities of the food do not produce any adverse reaction.  Some examples of foods which cause metabolic food reactions are sorghum, sprouts, bitter almonds, licorice, cycads etc.