Isotonic saline rinses the nose, but hypertonic will decongest.
If you buy an applicator, make your own saline with 3/4 tsp table salt in 8 oz tap water. If you're on a well or are unsure of your water supply, boil the water for 20 min and cool to room temperature. Some people like to add 1/2 tsp baking soda. If severe, talk with your allergist about the risks and benefits of nasal steroids