As many as two out of five Americans believe that they have allergies to certain foods. In fact, fewer than 2 percent have true food allergies. A food allergy occurs when the body's immune system reacts to otherwise harmless proteins in certain foods. While most food allergies are mild, in some cases they can cause anaphylactic shock, a serious, sometimes life-threatening, reaction. Food allergies affect mostly young children. With the exception of peanut allergy, the majority of children outgrow their allergic sensitivities.

A “Food sensitivity" includes all types of adverse reactions to food.

A "Food allergy" refers specifically to an immunological reaction.

Most of the literature focuses on immunologically-mediated mechanisms, especially that of food allergy (IgE), and it is likely that the majority of food reactions involve other mechanisms. These mechanisms include:

  • Hypoglycaemic reactions, especially to sugars and other refined carbohydrates

  • Non-IgE histamine release sometimes called pseudo-allergic reactions, such as to food additives such as tartrazine

  • Enzyme deficiencies such as are found in lactose intolerance, fructose intolerance, and sensitivity to dietary amines (deficiency of diamine oxidase)

  • Inappropriate binding of dietary lectins to cell walls or extra cellular molecules, such as wheat lectins binding to deficient IgG in rheumatoid arthritis

  • Neurotoxic molecules, such as glutamate

  • Pharmacological actions, such as from salicylate-rich food


  • Swelling or itching lips, tongue, and mouth
  • Dermatitis or hives
  • Runny and itchy nose
  • Headache
  • Stomach pain or upset (gas, bloating, diarrhoea)

The following allergy symptoms should be treated as a medical emergency:

  1. Immediate and extreme facial swelling and itching
  2. Breathing difficulties
  3. Rapid increase in heart rate
  4. Rapid drop in blood pressure
  5. Itching or tightening of the throat
  6. Sudden hoarseness


The foods that most commonly cause allergic reactions are peanuts, tree nuts (walnuts, pecans, and almonds), milk, eggs, soy, citrus, fish, shellfish, and wheat. In most cases, allergies occur when an individual who has a genetic sensitivity to certain allergens is exposed to the substance.

However a chronic intake of a certain type of food group can actually cause sensitivity to that particular food or food group and may show up as a delayed sensitivity which brings out the symptoms above 24 – 48 hours later.

It is well-documented that food allergy is an expression of an inherited genetic predisposition. Hence, allergic histories can often be found in both parents and siblings. One study discovered that when both parents are allergic, 67% of the children are also allergic. When only one parent is allergic, 33% are allergic.

Inadequate digestion of food products due to hypochlorhydria and / or pancreatic enzyme deficiency is also thought to be a significant cause of food allergies. Insufficient brush border enzymes such as lactase and sucrase also affect the body's ability to breakdown food to an elemental form.

When proteins are not digested completely, they retain their antigenic properties. These antigenic molecules may then be absorbed through a damaged mucosal barrier or "leaky gut" and exposed to the immune system. This in turn can create a state of chronic immune hypersensitivity and inflammation. In general, foods with a higher protein content (>20%) are more likely to be allergenic.

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