A food allergy is sometimes used to describe all adverse reactions to food, the term is more often used to refer specifically to food reactions that are mediated by the immune system.
To protect us from illness and disease, our immune systems protect us from illnesses and diseases so are continuously trying to lessen the danger represented by substances called antigens. Antigens are parts of proteins that our bodies recognize as dangerous and take steps to neutralize. Antigens can be found most anywhere there is protein – in foods, of course, but also in microorganisms like bacteria.
When our immune cells identify a dangerous antigen, they act to neutralize it and prevent it from causing harm in the body. When antigens from bacteria or viruses interact with our cells, we can get the flu, or the common cold. We don’t get the flu from food antigens, but we can get a wide range of immune-related symptoms that range from sniffles to hives to anaphylactic shock.
Immediate versus Delayed Hypersensitivity
Allergic reactions to food, also called food hypersensitivities, are further classified as either immediate or delayed. Immediate hypersensitivity reactions occur within hours or even a few minutes after a food is eaten, typically causing very obvious physical symptoms such as a rash, the hives, a running nose, or a headache.
In rare cases, immediate hypersensitivity reactions can cause anaphylactic shock, a life-threatening condition in which the throat swells and blocks the passage of air. Immediate hypersensitivities affect only a small percentage of the population.
Immediate Reactions to Food
The foods that are most often implicated as the cause of immediate allergic responses include milk, eggs, peanuts, tree nuts (walnuts), soy, strawberries, wheat, fish and shellfish. Many people with immediate food hypersensitivities must completely eliminate the offending food from their diet to avoid the serious symptoms.
Delayed Reactions to Food
Many of the same foods that are known to cause immediate hypersensitivities in a small number of people, have been implicated as a cause of delayed or “masked” food allergies in much larger numbers of individuals. Delayed food hypersensitivity reactions are believed to affect millions of people; some physicians have suggested that as many as 60% of all Americans suffer from masked food allergies.
These reactions may be responsible for a variety of symptoms including dark circles or puffiness under the eyes, fluid retention, dermatitis, sinus congestion, fatigue, abdominal pain or discomfort, joint inflammation, mood swings, indigestion, headaches, chronic ear infections, asthma, poor memory, anxiety and depression.
As the name suggests, delayed hypersensitivities do not appear immediately after consuming a particular food. In fact, in most cases the immune response is so delayed that it is difficult to determine which food is causing the symptoms, and many people are unaware that they are sensitive to certain foods.
Only through careful dietary manipulation, such as an Elimination Diet or Rotation Diet, is it usually possible to identify these hidden food allergies. The foods most often associated with delayed hypersensitivities include dairy products, eggs, wheat, soy products, peanuts, shellfish, and refined sugar.
Food Intolerance are immune-mediated food allergies represent one type of adverse food reaction. Another type of adverse food reaction is called food intolerance. Food intolerance is an umbrella term that refers to any abnormal physiological response to a food that is not caused by an antibody/antigen reaction. For example, some food intolerances are caused by enzyme deficiencies, while others are caused by poor function of the digestive tract or a sensitivity to a natural or synthetic chemical.
Lactose Intolerance is the most common food intolerance, which affects as many as 30% of adults, additionally it is particularly common in people of African and Asian heritage.
People with lactose intolerance do not produce enough of the digestive enzyme called lactase, which breaks down the milk sugar (lactose) found in dairy products. When too much undigested lactose makes its way into the large intestine, people suffer from gas and/or diarrhoea.
Wheat intolerance, wheat allergy, and wheat sensitivity are all terms frequently used to described adverse reaction to this food. Wheat is unique when it comes to adverse food reactions, particularly because it has long been classified as the primary “gluten grain” and because its research history has been both complicated and controversial. Understanding allergy-related issues associated with gluten is important for understanding problems connected to wheat.