I get this from time to time too, but I usually feel better after the foam is present. I tried the guaifenesin protocol for awhile to fight Chronic-Fatigue-Syndrome and fibromayalgia, and when I would high-dose the mucinex, I would expecially have high foam output. This was said to be the excrection of excess phosphorus, as people with CFS/fibro are supposedly poor excretors of phosphorus. This builds up and causes the fatigue and pain. I can't really say wether the protocol helped b/c it is difficult to follow. Many resrictions on supplements, personnal care products, gums, etc. It was so annoying! I had a hard time not slipping up. But I can say, when the urine was foamy--the days to follow were better than the days preceding the foam. I tried to view it as something yucky getting out.