Effective medication for this condition is available, and prophylactic treatment (topical corticosteroids, sodium cromoglycate) should be started two to three weeks before the pollen season to prevent priming by allergen. This year the warm spring has advanced the pollen season by two to three weeks and treatment should be started earlier. After concern over the risk of cardiac arrhythmias, the Medicines Control Agency is currently converting terfenadine, a commonly used antihistamine that is available over the counter, into a prescription only drug.