The famous case of cosmetic argyria Montalk mentions involves a Montana Senator named Stan Jones. Apparently, Mr. Jones was ingesting an inferior silver product that contained 100 PPM (parts per million) of silver, and eight ounces or more of this product daily for at least two years, when the recommended dosage is a tablespoon of a solution of about 3 - 4 PPM, with there being reports of even 5 - 20 PPM used to safely treat sinus infections without incident. There other factors that contribute to the risk of argyia, and one of them is a depletion of selenium after long-term use of colloidal silver.
It is quite possible, and even quite likely according to available research, that an individual can use 2 ounces of 10 PPM silver daily for fifty years and not incur any risk for argyria, and yet the same individual with a predisposition to the condition could take two ounces of a high PPM product, or eight ounces of an extremely poorly made product, and develop argyria in a few short years, when the product is used daily.
I've read that colloidal silver isn't nearly as effective swallowed as it is inhaled, as with a nebulizer, to treat something like a lung infection as the silver colloid must come in direct contact with the infection for the colloidal solution to have the greatest benefit.
The most comprehensive site I've found on colloidal silver can be found here:
with data on cosmetic argyria collected within the site here:
"Oh where have you been, my blue-eyed son? Where have you been, my darling young one?" - Roxy Music (B. Dylan)