Hay fever describes the symptoms of runny nose, itchy eyes and throat, uncontrollable sneezing and sometimes itching of the skin. It is not caused by hay, and does not produce fever. The correct name for the condition is seasonal allergic rhinitis. Many seasonal “colds” are actually allergic rhinitis and will not respond to antibiotics. Seasonal allergic rhinitis happens when pollens and/or particles of plant or animal dander, mold spores, etc., come into contact with the lining of the nose, eyes, or throat. The body’s immune system recognizes their presence and starts a reaction to prevent their invasion.
In most people this is not a problem. However, in some patients the immune system is overactive and identifies normally harmless particles as dangerous, producing an excessive reaction that actually causes inflammation. This is known as allergy and the substances causing it are allergens. People are allergic to only certain substances, and the reaction does not usually appear until after several exposures to that substance.