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 their neutralization.
In allergy sufferers, when a food is ingested, the body perceives something foreign and all its proteins are considered possible antigens.
Forms of food allergy
There are more forms of food allergy: "IgE-mediated" allergies (ie allergies mediated by antibodies called type E immunoglobulins) are certainly the most common and known 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 is a rather complex disorder, which can be summarized in several phases: sensitization, mast cell degranulation and release of chemical mediators.
- Sensitization : in this phase, which is completely separated from any symptom or clinical sign, the body first comes into contact with the allergen. Therefore, specific IgE will be produced towards that given antigen (the allergen, in this case, is represented by 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 is sensitized, a reaction is triggered which allows a faster antigen-antibody recognition.
- Mast cell degranulation : after the sensitization phase, any subsequent contact between the IgE and the food antigen (as occurs in all subsequent ingestions of the offending food) determines the degranulation of the mast cells to which the IgE have bound, resulting in release of histamine and other substances involved in the allergic reaction. Mast cells are ubiquitous in the body, but are found mainly in the nose, throat, skin, stomach and lungs, as they are more easily exposed to possible antigens, therefore more susceptible to the symptoms of allergic reactions.
- Release of chemical mediators : at this stage, adjacent to the previous one, the release of the chemical mediators responsible for allergy and inflammation occurs. These include histamine, a veritable "biological bomb" freed from the degranulation of mast cells: it should be remembered, however, that histamine remains silent until the antibody is in contact with the allergen .
Causes
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 pathologies, immunosuppression and mal-absorption of the gastro-intestinal mucosa.
Considering that all the proteins contained in foods can be perceived as foreign substances (and therefore potentially dangerous), and that a subject cannot survive without food, in the healthy organism a mechanism must be established for which every food antigen is interpreted as “substance extraneous but harmless ”. Under normal conditions, proteins are broken down into amino acids and, therefore, digested thanks to gastric and pancreatic enzymes: an absorption of the 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.
Food allergies, unlike intolerances, are dose-independent: this means that even a small amount of allergen is enough to trigger the allergic reaction, which can also occur in very violent forms, such as anaphylactic shock.
Symptoms
The symptoms associated with a food allergy are mainly due to disorders affecting the digestive system, mucous membranes, skin and respiratory tract.
Stomach pains, diarrhea, swelling of the skin (itching and redness), respiratory and cardio-respiratory problems are the most common symptoms, up to anaphylactic shock; the general symptoms caused by an allergic disease are summarized in the table.
| ZONE HIT | SYMPTOMS |
Skin | Edema Eczema Itching / hives Inflammation and swelling |
Respiratory tract | Asthma Rhinitis Allergic cough Laryngeal edema |
Gastro-intestinal tract | Abdominal pain Diarrhea enteropathy Nausea / vomiting Blood in the stool Itching in the pharynx Oral allergic syndrome |
General manifestation | Hypotension Anaphylactic shock Fatigue Migraine Ear infection Hyperactivity |
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 is sensitized.
