Some of the Physio

As mentioned before, the overall concept of hay fever is caused by the bodies sensitization to a specific allergen. But how exactly is this caused?

Our immune system is made up of several structures; this includes skin and mucous membranes, the mononuclear phagocyte system, the lymphoid system, and bone marrow which all have different types of white blood cells, also known as leukocytes. Leukocytes help protect the body through inflammation and immunity.  T Lymphocytes (or T cells) are the mediators of specific immunity which act by reacting to the presence of a specific antigen (marker of a foreign substance) body and stimulates B Cells to make antibodies, a protein complex which react to the antigen.

In hay fever this antigen is caused by the presence of an otherwise substance that isn’t harmful. This is an allergen that after repeated exposure causes a hypersensitive reaction. The primary antibody responsible for mediating this reaction is immunoglobin E, or IgE. The IgE binds to receptors on other cells in the immune system known as mast cells. This IgE Mast Cell complex can bind to passing antigens (the specific allergen) and create a crosslink (when two antibody ends attach to an antigen) therefore causing an increase of intracellular calcium in the mast cell. This increase causes local mast cell degranulation resulting in the symptoms of inflammation. This may cause other inflammatory cells, and as for the case of hay fever, basophils to also release chemicals. The primary receptors to these are histamine. (That is why a lot of allergy medications are classified as antihistamines). Histamine causes a variety of symptoms, which may vary in severity. Some of the effects of histamine include bronchoconstriction, vasodilatation, increased mucus secretion, and pruritus (itching).

This however depends how the allergen entered the body and how much. For those with hay fever the most common is the allergic rhinitis (because the allergen enters through the nasal passageway). These symptoms also occur only when the allergen is present (or in high enough levels) for the antibodies to react. That is why for those with seasonal allergies they vary on location and pollen levels and for those with chronic have to make lifestyle changes depending on the cause.