Diarrhea, loose stools
Musculoskeletal, joints, muscles, connective tissue
Inflammatory myopathies, myelopathies
Joint discomfort, pain, stiffness, swelling
Food is obviously the foundation of nutrition and its quality and quantity will determine how healthy or how sick an individual will be. But what happens when one has an adverse reaction to the very thing they require to live? Basically, an adverse reaction to food appears to be either toxic (e.g. food poisoning) or non-toxic. A non-toxic adverse reaction takes one of three forms:
Food allergy, food intolerance, or food sensitivity.
Food allergy is mediated by IgE antibodies (specific adaptive immunity) and may be so severe as to be life threatening (e.g. anaphylactic shock). This type of reaction is considered a “classic allergy” or “type 1 hypersensitivity reaction.”
Food intolerance refers to an inability to metabolize, digest, or absorb a food component (e.g. lactose intolerance due to lack of lactase enzyme). A pathophysiological food intolerance does not involve the immune system. Food intolerance symptoms tend to be confined to the GI tract (gas, bloating, abdominal distension).
Food sensitivity is currently defined as an adverse reaction to a food that is not due to an IgE- mediated reaction or a metabolic deficiency. It does, however, appear to involve an immune inflammatory reaction that may be local or systemic. Food sensitivities may also be referred to as delayed food hypersensitivities or even “hidden food allergies.” 
For simplification, consider that food intolerance refers to non-immune based reactions while food sensitivity refers to immune- based reactions that are non-IgE mediated. The terms food intolerance and food sensitivity have been used interchangeably in the past so don’t be surprised if you feel bewildered. Also keep in mind that some food sensitivity symptoms may mimic food allergy, so it is important to rule out IgE-mediated food allergies when assessing for sensitivities.
This FYI focuses on food sensitivity testing and the most current research behind available testing methods. It does not address food intolerance or food allergy.
An adverse reaction to a food is often noticed because of the distressing nature of the symptoms, especially those that are gastrointestinal (GI) neurological, respiratory, or dermatological in nature. See “Signs and symptoms of food sensitivities.”
Ref: Cell Science January 2018