frequent nosebleeding

Any special treatment, or prevent it from reoccurring?

My 7 year old boy began to have frequent nose bleeding since we moved to LA five years ago, on and off. Recently , it seemed to get worse, at least once a week, today the school nurse called me because it was lots of blood coming out. We checked with doctor and was told to use nasal spray (with salt in it).

Any other suggestions. Thanks a bunch.