Its kinda difficult for me to use- I have Asthma and CF- but I feel that it helps alot (more sputum and decreased viscosity). But I have heard that people with more severe asthma could have serious problems with hypertonic saline (bronchospasm/hemoptysis). I was actually taken off it for a while since I coughed all day if I took it in the morning. But I am on it again (the highest concentration too lol)