Hello, Nasal irrigation For chronic sinusitis it can be an effectve add on therapy. It relives congestion but it's not mainstay treatment. Antihistamines effectively treat allergies, You can use decongestants over a short period of time to help relieve stuffy nose and sinus pressure. immunotherapy also suggested by doctors. The best way to prevent allergy symptoms is to manage your allergies before your body has a chance to adversely respond to substances.