Hay fever is an allergic reaction to pollen which triggers symptoms such as sneezing, runny nose and inflamed eyes. The condition can be treated with antihistamines or steroids (for extreme cases), or in cases where the sufferer is allergic to one specific variety of pollen, by desensitisation. This involves injecting the patient with small quantities of the substance to which they are allergic (the allergen) at regular intervals. This causes antibodies to be produced in the bloodstream, which combine with the allergen during subsequent exposures, preventing the symptoms from occurring. In Britain, the main cause of hay fever is gras pollen, and it is estimated that between 15 and 20 % of the population suffer from the condition to some degree.
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