Food Allergies and Sensitivitieseggs

Food allergies and sensitivities are illnesses that affect certain individuals when eating foods or food ingredients that most consumers can tolerate with no problem.

These illnesses are sometimes called individualistic adverse reactions to foods because they affect only certain individuals in the population. Many different illnesses occur that fall under the broad definition of food sensitivities.

Food allergies include immediate hypersensitivity reactions (an example would be food allergy to peanut) and delayed hypersensitivity reactions (an example would be celiac disease). peanust

In all cases, the most common form of treatment is implementation of an avoidance diet – simply avoiding the food or food ingredient that elicits the adverse reaction. But the degree of care needed to implement a successful avoidance diet can depend upon the nature of the illness, so it is important for physicians to perform a differential diagnosis and for consumers to know which type of illness that they have.

Many different illnesses occur that fall under the broad definition of food sensitivities. Many consumers and some physicians and other health professionals refer to all of these illnesses as food allergy. But no matter what term is used, it is important to recognize that many different types of illnesses occur due to foods and food ingredients on an individualistic basis. These different illnesses can require different diagnostic strategies.

Food allergies are abnormal immunological responses to a particular food or food component, usually a naturally occurring protein.

Two types of abnormal immunological responses can occur - immediate hypersensitivity reactions and delayed hypersensitivity reactions. Both are well documented to occur in certain individuals upon ingestion of specific foods. See list of the 8 most common.

  • Immediate hypersensitivity reactions are IgE-mediated reactions with symptoms ensuing within minutes of the ingestion of the offending food.
  • Delayed hypersensitivity reactions are cell-mediated reactions with symptoms developing 48 – 72 hours after ingestion of the offending food. Celiac disease is the best example of a delayed hypersensitivity reaction associated with foods.

The role of cell-mediated reactions in food allergies is far less well established; IgE-mediated food allergies by contrast are quite well understood. Both reactions are discussed in more detail in the pages linked below:

  • IgE-Mediated Food Allergies

    IgE-mediated food allergies are true food allergies involving an abnormal response of the immune system to one or more specific foods.
  • Symptoms

    A number of different symptoms can be associated with IgE-mediated food allergies. The symptoms of IgE-mediated reactions can involve the gastrointestinal tract, skin, or respiratory tract. Some symptoms of food allergy are potentially quite severe, with anaphylactic shock being the most severe.
  • Prevalence of Food Allergies

    IgE-mediated food allergies affect an estimated 6 - 8% of infants and children and 2 – 3% of adults in the United States.
  • Diagnosis and Treatment of Food Allergies

    The major approach to the treatment for true food allergies is their prevention their occurrence through implementation of a specific avoidance diet.

3 distinct forms of food intolerances are recognized:

In contrast with food sensitivities, individuals affected by food intolerances experience adverse reactions from eating typical amounts (or even some times far less) of a food or food ingredient that most consumers can ingest with impunity.


Food intolerances are adverse reactions to foods or components of foods that do not directly involve the immune system.

The adverse reaction to the food is often a result of inherent factors of the food or genetic defects of the affected individual. Sensitive individuals can often tolerate some amount of the offending food, unlike food-allergic individuals who can have reactions to minute amounts of the offending food. 

Metabolic food disorders are one example of a food intolerance and are not the result of a disorder of the immune system. Metabolic food disorders result from a genetically-inherited defect in the ability to metabolize a food component or a genetically-inherited sensitivity to a food component that affects some critical metabolic process.

Idiosyncratic illnesses are adverse reactions to foods that occur through an unknown mechanism(s) resulting in a wide range of symptoms ranging from mild skin irritation to life-threatening reactions.