Mrs J,
Although it is alright to use this nasal spray for several days, longer term use can actually cause the nasal receptors to adapt and the passages may even swell up more. I would suggest asking his doctor for a nasal steroid (triamcinolone works great) for allergic rhinitis, which is what this sounds like. Use it twice a day in both nostrils, the dose may need to be increased slowly if there is only a small amount of improvement over a few weeks. It typically takes 2-3 weeks to see some effect because the inflammatory cells need to be shut down.
--Dr. Sun