With the recent hysteria in the U.S. concerning anthrax, many of the companies that sold colloidal silver as a cure-all have naturally taken advantage of the situation, proclaiming it as a preventative agent. Whether or not you believe in this solution, however, take heed of the character of the companies selling to you. QuackWatch reports that in a 1995 study of nine different commercially-available solutions, two of them were contaminated with microorganisms, only five actually showed any antibacterial activity whatsoever, and all of them varied wildly in concentration. Colloidal silver intake can also lead to a condition known as argyria, or silver poisoning, in which skin and fingernails can actually take on a blue-gray or silvery hue.