My father in law uses the nasal rinse more than 10 times a day. Is this healthy? What kind of health issues can this cause?

I am not sure why he needs to use this several times a day. I doubt that it will create any harm but it may be unnecessary. Please have him see his ENT doctor and see what would be ENT doctor's comments. Also, does he feel that mucus builds up very fast and he needs to do the rinse. In that case one needs to find out the root cause why mucus is formed in the first place.