Laboratory of clinical and microbiological analysis

Food  allergy and intolerance

The term ”food allergy ”consist of a series of clinical symptoms that are very much like those of intolerance, therefore, the two are often confused. Despite some authors calling into question their existence, these pathologies are on the increase because changes in our eating habits have occured.

In our markets we can find fruit, vegetables, meats, fish, which come from all over the world; there isn’t “the cycle of the seasons” anymore, because between cultivations in greenhouse and imports we can find the same products all year round.

In consequence, we are finding an ever increasing number of “preservatives, antioxidants, additives, etc” to which humans have no antibody protection. Nowadays, this is a big problem, because it isn’t easy to differentiate if the symptoms of an allergy or an intolerance are due to food-stuffs or additives.

By “allergy” we mind an “irregular” response by an organism to a substance (antigen) normally harmless to healthy people. The antigen, often of proteinic nature, excites the production of specific antibodies in the organism, in which it introduces itself.

An antigen that  comes into contact with an antibody and starts to reveal allergic phenomenons is called  an “allergen”.

Most “hypersensitivity” that occurs in an allergic subject is due to immunological interactions between antigens and humoral antibodies or sensitized lymphocytes.

By convention , the allergic reactions follow the classification of Gell and Coombs:

These are due to Ig E antibodies that attach themselves to mast cells and basophilis.

When Ig E bind themselves to the allergen there is a rapid release of chemical substances (histamine, tryptasi, cytokines, etc.) that also attract eosynophilis, wich are other blood cells.

In this category are included: allergic asthma, seasonal rhinitis, sinusitis, otitis, conjunctivitis, urticaria, some reactions to drugs. etc

Allergy peculiarity uses the appearance of a clinical manifestation within a short time: from 5 min. to 2 hours or more from the introdution of the “harmful” foodstuff. The quantity of food necessary to cause an allergic reaction varies from one person to another, and if an individual is very sensitive, even a small quantity can be dangerous: for this reason it is said be an “independent-quantity” mechanism.

After you introduce fruit and uncooked vegetables, a localized reaction of itching and edema of the lips, as well as of the palate might appear. It can cause gastrointestinal pathology with: vomiting, diarrhea, swelling, edema of oropharingeal cavity, etc. The pathology caused by urticaria can manifest after introducing fish, shellfish, peanuts, fruit, milk, egg.

The atopic dematitis is typical in young children.

The most severe reaction that might occur is the “anaphylactic shock”, that appears with a severe drop in arterial pressure, loss of conscience ness and diffused edema.

There is a type of anaphylaxis caused by physical effort that is associated to a particular food-stuff. The patient isn’t aware of being allergic to the food-stuff because, in normal conditions, he doesn’t have any reaction; until he has praticed a sport that has activated a series of allergic manifestations.

Non -Ig E mediated Reactions that include:

-Type II° Reactions also called cytolitic and/or cytotoxic:

These are mediated by antibodies Ig G and/or Ig M that bind themselves to cellular structures injuring them. In this category are included allergies to drugs, hemolitic anemia, etc.

- Type III° Reactions or immunocomplexes reactions:

These are due to a depositing, on the near vessels and tissues, of soluble antigen-antibody complexes and they are responsible for vascular, renal lesions, etc. causing “serum sickness “, thrombocytophenia, vasculitis.

- Type IV ° Reactions or mediated cells reactions:

These are the consequence of the action of activated lymphocites that react with the allergen, releasing toxic substances. They are responsible for contact dermatitis, photoallergic reactions, thrombocytopenia, enteropathy from glutine.