Food Allergy Type I

Food Allergy Type I
Food Allergy can be defined an adverse reaction to a food or food component (often a protein) involving reactions of the body’s immune system (immunological reactions). The term “food allergy” should only be used to identify true, immunological based food allergies – those which affect the body’s immune system. Examples would be allergy reactions to common foods such as cow’s milk, eggs, peanuts, and many others. It is preferred over the alternative term “food hypersensitivity,” which has been used to describe this type of reactions, as well as other types.

Allergic response may be organized into four categories noted as Types I – IV

Type I Allergies
This type of allergies is also known as food anaphylaxis. The Greek word anaphylaxis and refers to allergic reactions to foreign protein molecules. This may be the best understood area, scientifically speaking. Immediate hypersensitivity type allergic reactions appear to fall entirely within the category. Type I reactions usually occur within a few minutes to several hours after consumption of the offending food. The observed symptoms of type I hypersensitivity result from the release of pharmacologically active substances such as histamine. This occurs from specific cells in the body known as mast cells, as a consequence of interaction between Immunoglobulin E (IgE) and food substances which cause allergic reactions (allergens).

IgE is one of five antibody immune systems which work in the human body to resist disease, functioning as specific antibodies. Mast cells are present in many tissues and generate histamine, the substance associated with allergy symptoms, although the cells specific physiological function is not fully known.

Exercise-induced food anaphylaxis is a subset of food anaphylaxis that involves reactions that occur only when the specific food is ingested just before or just after exercise. On the other hand, many cases of exercise induced anaphylaxis are not related to foods.
Food Allergy Type I

What are the anaphylactoid reaction symptoms?

Anaphylaxis was first reported in 902 by Portier and Richer when immunizing against jellyfish toxins with actinia extract. Instead of transferring immunity, some of the animals developed marked shock, which resulted in death.

Anaphylactoid reaction is an acute hypersensitivity reaction which shows the symptoms of an anaphylactic reaction, and it is not immunological reactions.

It has been used to describe all clinical reactions patterns mimicking anaphylaxis without describing pathophysiological mechanism.

The principal manifestation of anaphylaxis occurs in areas where mast cell concentrations are highest: skin, lungs and gastrointestinal tract. Histamine release is responsible for the clinical manifestations of this reaction.

The clinical symptoms of anaphylaxis often start with skin symptoms (itch, flush, urticarial, angioedema) and can comprise respiratory, gastrointestinal, and cardiovascular symptoms.

Symptoms of anaphylaxis occur within 2 to 20 minutes of exposure to the antigen or hapten and may persists for up to 36 hours.
What are the anaphylactoid reaction symptoms?

Type I food allergy mechanism

Four distinct types of hypersensitive reactions – types I, II, III, IV are recognized and each type involves different components of the immune system.

What is type I allergies?
This type of allergies is also known as food anaphylaxis. The Greek word anaphylaxis and refers to allergic reactions to foreign protein molecules.

These reactions are the most frequent, the best known and the easiest to diagnose. They occurred when an individual is already sensitized.

Immediate hypersensitivity type allergic reactions appear to fall entirely within the category. Type I reactions usually occur within a few minutes to several hours after consumption of the offending food. It is the common allergy that can largely be attributed to IgE and a sub-population of immune cells, the mast cells and basophilis.

IgE antibodies will bind the allergen and this will lead to mast-cell degranulations and release of mediators such as histamine and the characteristic features of allergy include:
*urticaria
*angioedema
*hypotension
*anaphylaxis

Immediate type allergy is usually obvious to everyone who suffers from it and afflicts about 10% of the population. The immediate or type 1 food allergy pattern is easily recognized because it involves quick and dramatics symptoms.

Patients who tend to have type 1 reactions are easily identified by their history; they tend to have hay fever, asthma and eczema as do family members. These triads of allergic manifestations had been called ‘atopy’.
Type I food allergy mechanism