Anyone regularly using humidifiers need to completely sterilize them throughout. After months of use they build up molds, bacteria etc. Constantly using them has caused cold symptoms which I guess are simply an immune response to the over loading invasion of the molds and bacteria you are breathing all night from the humidifier.
I used the MMS bath tablets, cut one in half and dissolved it in a large glass, pour it in the humidifier, fill it up with water, and let it soak for a good 20 min. Then I started running the humidifier in the same room overnight.
My son had a chronic nasal infection/cold type infection which his grandmother thought was from being cold or having a standard cold. After purifying it, and running the chlorine dioxide in his room that night, the next day he was 50% better and the second day completely back to normal.