Some Colloidal Silver has or is apt to grow mold within the molecule or within the preparation. I researched this extensively [mostly but not entirely online]several years ago and do not recall the details now. If you feel you need Colloidal Silver for your health it is important to research the manufacture of CS enough to be sure you are choosing a CS that is mold free. Sorry I do not have the details for you but as I understand it mold is a valid issue with CS. The presence of mold might make some problems worse.