What is Food Allergy, Food Intolerance,

and Food Sensitivity?


Food Allergy

We all know about food reactions that can trigger immediate, severe responses such as hives, swelling of the lips, tongue, and throat, and even breathing difficulties. These types of reactions, known as anaphylaxis, are caused by IgE-mediated true food allergies that trigger the immune system’s release of huge amounts of histamine into the body causing immediate inflammation, itching, and contraction of smooth muscle cells in the blood vessels (increasing blood pressure), gastrointestinal tract (cramping), and respiratory tract (difficulty with breathing). This is the same immune mechanism that occurs in people who are allergic to pollens, mold spores, certain drugs, and bee venoms. True food allergies affect about 6-8% of infants and children and about 2-3% of adults in the United States.


The eight most common allergenic foods (dubbed the “Big Eight”) that account for 90% of all IgE-mediated food allergies are

  • peanuts
  • soybeans
  • cow’s milk
  • eggs
  • tree nuts
  • wheat
  • fish
  • shellfish


Food Intolerance

A food intolerance is a broad term for adverse food reactions in which something in a food irritates a person’s digestive system or when a person is unable to properly digest the food possibly due to a lack of the enzyme needed to properly do so. Food intolerance reactions do not involve the IgE-mediated release of histamine like in food allergy reactions.


One of the most common example is lactose intolerance. These individuals lack the enzyme, lactase, to break down, lactose, the sugar found in cow’s milk. In such situations, the lactose is broken down by gut bacteria producing gas which results in bloating, abdominal cramping or pain, and sometimes even diarrhea.


Food intolerances can also be caused by ingestion of tyramine, gluten, and preservatives and food additives such as MSG, food colorings, and sulfites. Symptoms may include abdominal gas, cramps, bloating, heartburn, headaches, and irritability or nervousness. The severity of the symptoms may also be dependent on the amount of the food consumed.


Food Sensitivity

Food sensitivity is a category of food reactions whose exact definition varies depending on context and with different medical professionals. Some use it as an umbrella term to include both food intolerance and food allergy. Others use the term to describe toxic reactions like food intolerances that are not IgE-mediated food allergies. Similar to food intolerances, food sensitivities can cause vomiting, diarrhea, eczema, hives, dermatitis, runny nose or sinus congestion, wheezing, and blood in the stool. However, food sensitivities can also cause extremely vague symptoms such as fatigue, gas, bloating, mood swings, anxiety, nervousness, headaches and other neurological issues. These symptoms can appear up to two days after consuming the offending food or symptoms can also become chronic due to continuous consumption of that food. Moreover, cross-reactivity can occur with seemingly different types or ranges of food. For example, people with gluten sensitivity may also find they have a sensitivity to casein, the main protein in cow’s milk. 


The Bottom Line

The blurred bottom line can definitely be confusing but what is more important than the label is finding the possible foods that could be making you sick.