Nasacort Allergy Nasal Sprayworks to relieve allergy symptoms for up to 24 hours. The spray is thixotropic which means it stays where it is sprayed so it works where it is needed the most – in the nose. It has an anti-inflammatory action which brings quick relief from allergy symptoms such as sneezing, congested nose, itchy nose and runny nose.How to use Nasacort Allergy Nasal Spray: Shake the bottle gently before use. Use only in the nose Adults aged 18 or over - 2 sprays in each nose once daily. Once symptoms improve use one spray in ach nostril daily.Children - not for use in children under 18 years. Relief may be obtained on the first day of use but it my take up to 4 days for maximum effect.