i never have had any problems using the Navage, i do know you need to use distilled water and do not have it too hot/warm...that can cause issues with the capillaries in the nose..my phlegm is more the color of elmers Wood glue, yellow..and sticky like that...an ENT suggested sinus surgery which i won't do, it's only a temporary fix...for me..keeping my sinuses flushed helps to keep it from building up too thick to the point of throwing up, gagging, airway blocked...so on. i know covid has really made my sinuses a mess and the ENT says the are chronic....it's always a mess right after i eat or drink anything, other then building my immune system, i'm planning to check my acid/alkaline ph. i know having a ph with too much acid can not be good...if possible i will use medication as a last thing....i refuse to letting this demon virus win...hope to all, we have a mess to get through,,,HUGS!!!!