Food allergies: causes and symptoms

Food allergy: definition

An “allergy” is defined as an exaggerated and violent reaction triggered by the immune system against substances, called antigens, to which it is particularly sensitive . Antigens, or rather allergens, are substances that the body recognizes and interprets as foreign and potentially dangerous, therefore deserving of an immune attack aimed at neutralizing them.
More specifically, we speak of food allergy when one or more substances contained in a food are recognized as potentially dangerous for the organism itself: consequently the antibody system triggers an often violent immune response.
In allergic subjects, when a food is ingested, the body perceives something foreign and all its proteins are considered possible antigens.

Forms of food allergy

There are several forms of food allergy: “IgE-mediated” allergies (ie allergies mediated by antibodies called type E immunoglobulins ) certainly represent the most known and common allergic form. Then there are also other types in which other types of antibodies are involved, such as IgG and IgM.

How it manifests itself

Food allergy represents a rather complex disorder, which can be summarized in several stages: sensitization, mast cell degranulation and release of chemical mediators.

  1. Sensitization: in this phase, which is completely separated from any symptom or clinical sign , the organism comes into contact with the allergen for the first time. There will then be the production of specific IgE towards that given antigen (the allergen, in this case, is represented by the food proteins). These immunoglobulins bind to certain receptors placed on the surface of mast cells; in this way when the subject again ingests the food to which he has become sensitized, a reaction is triggered that allows faster antigen-antibody recognition.
  2. Degranulation of mast cells: after the sensitization phase, each subsequent contact between the IgE and thefood antigen(as occurs in all subsequent ingestions of the offending food) determines the degranulation of the mast cells to which the IgE are bound, with consequent release of histamine and other substances involved in the allergic reaction. Mast cells are omnipresent in the body, but they are found mainly in thenose, throat,skin,stomachandlungs, as they are more easily exposed to possible antigens, therefore more susceptible to the symptoms ofallergic reactions.
  3. Release of chemical mediators: in this stage, contiguous to the previous one, the release of the chemical mediators responsible for allergy and inflammation Among these we remember histamine, a real “biological bomb” released by the degranulation of mast cells: it is good to remember, however, that histamine remains silent until the antibody comes into contact with the allergen .


The main causes that can trigger an allergic reaction to a given food can be related to various factors: continuous exposure to the allergen, heredity, environmental agents, viral diseases , immunosuppression and malabsorption of the gastrointestinal mucosa .
Considering that all the proteins contained in food can be perceived as foreign substances (therefore potentially dangerous), and that a subject cannot survive without food, a mechanism must necessarily be established in the healthy organism by which each food antigen is interpreted as a “substance. extraneous but harmless “. Under normal conditions, proteins are broken down into amino acidsand, therefore, digested thanks to gastric and pancreatic enzymes : an absorption of amino acids by the intestinal mucosa will follow . The phenomenon of “tolerance” has just been described, thanks to which a subject can eat a food without problems.
If this system is compromised, food allergy is triggered.
The food allergies , in contrast to the intolerance , are dose-independent, which means that even just a small amount of allergen to trigger an allergic reaction, which can occur even in very violent forms, such as anaphylactic shock .


Symptoms associated with a food allergy are mainly attributable to disorders of the digestive system , mucous membranes , skin, respiratory tract.
Stomach pain , diarrhea , swelling of the skin ( itching and redness), respiratory and cardio-respiratory problems are the most common symptoms, up to even anaphylactic shock; the table summarizes the general symptoms caused by an allergic pathology.


Skin Edema
Pruritus / hives
Inflammation and swelling
Respiratory tract Asthma
Allergic cough Laryngeal
Taken gastro-intestinal Abdominal pain
Nausea / vomiting
Blood in stool
Itching of pharynx Oral allergic
Generalized manifestation Hypotension
Anaphylactic shock


Table taken from the book “Dietetic Products: chemistry, technology and use”, F. Evangelisti, P. Restani, piccin publisher.


The only effective remedy to avoid the manifestation of the unpleasant symptoms of food allergies is the elimination from the diet of the food to which the person has become sensitized.


by Abdullah Sam
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