Nasacort Allergy Nasal Spray contains triamcinolone acetonide – an ingredient that has been used by doctors to treat allergies for many years, but is now available as a nasal spray for hayfever directly from your chemist without a prescription. Nasacort Allergy prevents the release of the chemicals that cause hayfever. It is effective against all hayfever symptoms and starts to get to work on the first day of treatment, though it may take a few more days to reach its maximum effect. You should keep taking Nasacort Allergy throughout the hayfever season for maximum benefit but you should see your doctor if you have to take it continuously for more than 3 months.