1. Yes, infact while swimming the water entering nostrils will wash away some of the allergens inhaled by you, and it strengthens your airways, so that your immune system is in a better position to handle any illnesses. 2. Surgery for DNS is merely the first step in the treatment of Allergic Rhinitis. This makes way for medications in the form of metered dose nasal sprays to treat the allergy. Ultimately, you will need to undergo Skin Prick Tests for Allergy to identify the allergens that your immune system has been sensitised to and undergo immunotherapy for the same. 3. Army and Airforce: yes unless you have Sinonasal Polyposis. During the bout of allergy, you will be grounded from flying duties till your Airforce Doctor certifies you fit to fly. Many over the counter medicines are forbidden for pilots. Only those prescribed by your Airforce Doctor to be used.