- A metabolic reaction: Food intolerance, also known as a non-allergic food hypersensitivity, is an inherited inability to metabolize (digest) certain foods, such as fat or lactose (the naturally occurring sugar in milk). The reaction may include intestinal gas, diarrhea, or other signs of gastric revolt.
- A physical reaction to a specific chemical: Your body may react to things such as the laxative substance in prunes or monosodium glutamate (MSG), the flavor enhancer commonly found in Asian food. Although some people are more sensitive than others to these chemicals, their reaction is a physical one. It doesn't involve the immune system.
- A body response to psychological triggers: When you're very fearful or very anxious or very excited, your body moves into hyper drive, secreting hormones that pump up your heartbeat and respiration, speed the passage of food through your gut, and cause you to empty your bowels and bladder. The entire process, called the fight-or-flight response, prepares your body to defend itself by either fighting or running. On a more prosaic level, a strong reaction to your food may cause diarrhea. It isn't an allergy; it's your hormones.
- A change in mood and/or behavior. Some foods, such as coffee, contain chemicals, such as caffeine, that may cause hyperactivity, as well as having a real effect on mood and behavior.
