Last Updated on Monday, 19 October 2009 10:36

Causes of Hay Fever

Hay fever results from an allergic reaction to substances like pollen and fungal spores when they come into contact with the upper respiratory tract (nose, sinuses, and throat) and the eyes. Your immune system produces antibodies against these allergens, perceiving them as harmful, thereby precipitating the release of chemicals like histamine into the bloodstream. Histamine is what produces the classical symptoms of hay fever.

Sufferers are allergic to one or many pollen varieties. Common types include:

• Grass pollen – Commonest offending allergen in the UK, 9 of 10 people being allergic to it. Symptoms are worst from May to July.

• Tree pollen – Commonly pollen from birch trees. Allergies set in during spring.

• Weeds and other plants, as well as fungal spores – These commonly produce symptoms from June or July to November.

Pollen seasons vary from place to place, commencing earlier in the southern parts of UK than in the north, where it continues late into the year. The number of pollen grains present in each cubic metre of air influences the severity of symptoms and represents the pollen count. This is at its highest at about 5 to 6 PM in the countryside, and somewhat later in urban areas. Weather conditions also determine the amount of pollen released from flowers and the distance it travels.

A family history of allergies may increase your risk of developing hay fever.