What is the mechanism of an allergic reaction?

The mechanism of IgE-mediated food allergy comprises of a two-step process. After the first contact with the food allergen, the allergen will be attached to antigen-presenting cells, which will in turn present the antigen to T-cells. These T-cells then stimulate B-cells to produce antibodies specific to the antigen, the specific immunoglobulin E or IgE. These antibodies will be bound to IgE receptors present on mast cells. This process is called sensitisation. After the next exposure to the food allergen, mast cell-bound IgE recognises the allergen and gets cross-linked, followed by a release of mediators which in turn cause allergic reactions.  If this allergen is milk protein, for example beta-lactoglobulin, we call it cow’s milk allergy.