Food Allergy

General Information






What is a Food Allergy?

Mast Cell

A food allergy is an immune system response to a food that the body mistakenly believes is harmful. Once the immune system identifies a particular food as harmful, it creates specific antibodies (specific IgE) to it. The next time the individual eats that food, the IgE attached to a cell (mast cell) stimulates the release of massive amounts of chemicals, including histamine, in order to protect the body. These chemicals trigger a cascade of allergic symptoms that can affect the respiratory system, gastrointestinal tract, skin, or cardiovascular system.  This is an overreaction of the immune system not a weakness or immune deficiency.  In allergic reactions the immune system is working perfectly normal.  The abnormality is with an error in recognizing the food protein as foreign.
    IgE, mast cells and other components of the allergic cascade are an important part of our immune system.  These components are how we fight off parasitic diseases.





What are the symptoms of food allergy?

Immediate reaction (usually with in 2 hrs, but can happen up to 24hrs after exposure):

  • tingling sensation in the mouth
  • Swelling of the tongue and the throat
  • Difficulty breathing
  • Hives
  • Vomiting
  • Abdominal cramps
  • Diarrhea
  • Drop in blood pressure
  • Loss of consciousness
  • Death

Reaction days later: (A mixed reaction or T-cell reaction (no IgE involved )

  • Eczema (atopic dermatitis)
  • Fatigue
  • Reflux (heartburn)
  • Chest pain
  • Abdominal pain
  • Nausea, vomiting
  • Poor weight gain or weight loss
  • Difficulty swallowing solid food (dysphagia)



Are food allergies permanent?

Early childhood allergies to milk, egg, wheat and soy resolve in approximately 80%.

Peanut allergy resolves in 5% of children by age 5 (it may reoccur) and 20% by teenage years.

Typically food allergies with significant reactions (i.e. anaphylaxis) resolve at a much lower rate.




Are all adverse reactions to foods an allergy?

Food Intolerances are common-

  • Food poisoning: derived from food contaminated with bacteria and bacterial toxins.
  •  Histamine toxicity: high levels can be found in cheese, some wines, and fish in the scromboid family (tuna, mackerel).
  • Scromboid poisoning- Fish from the scromboid family is not refrigerated properly and contaminated by a bacteria.  This bacteria feeds on the meat and  produces histamine.
  •  Lactose intolerance: due to lactase deficiency (an enzyme in the GI tract).  The lack or deficiency of lactase inhibit the ability to break down lactose (the sugar in milk).  Un digested lactose is digested by bacteria causing gas production, abdominal pain and diarrhea.
  •  Food additives:  MSG and sulfites are two examples
    • MSG: in large doses can cause: flushing, sensations of warmth, headache, chest discomfort, feeling of detachment.
    • Sulfites occur naturally in foods or may be added.  Sulfites once ingested and in the stomach can give off a gas called sulfur dioxide.  In high concentrations asthmatics can inhale this gas while eating, causing an asthma attack (bronchospasm)





Most Common Food Allergies

Children (6%-8% of all children have food allergies):

  • Cow's Milk (2.5%)
  • Egg (1.3%)
  • Peanut (0.8%)
  • Wheat (0.4%)
  • Soy (0.4%)
  • Tree nuts (0.2%)
  • Fish (0.1%)
  • Shell fish (0.1%)

 Adults (4%):

  • Shell Fish (2%)
  • Peanuts (0.6%)
  • Tree nuts (0.5%)
  • Fish (0.4%)

*Sesame seed is now a member of the most common food allergies.


Reactions to Fruits and Vegetables are common (5%) but are usually not severe


 A person can be allergic to just about any food. 


 Many reactions to foods are not an allergy but an intolerance.