This humidifier seemed to work really well for the first few days. But after the 3rd or 4th day, I noticed a lot of mildew growing inside the unit. So, I cleaned the unit almost daily, but despite my scrubbing, it always came back (no big surprise, I suppose... heat + water + dark enclosed space = mildew). In fact, it was stained onto the unit so badly that no amount of scrubbing seemed to get rid of it all.The problem is, I think I may have developed a bacterial infection from the mildew. I can't be sure, of course, since this is flu season. But I couldn't shake this sore throat and congestion for weeks. Then after a round of antibiotics, it went away. Soon after, I started using the humidifier again... and lo and behold, my symptoms returned.It's not a definite correlation, but I'm definitely NOT going to use this thing anymore.