Would this particular case be Rosemary Jacobs by chance? If so, then I'd add that the spray she used is what is referred to today as a Silver Nitrate(or protein). Of which concentrations were known to start in the 1500 ppm range(for mild solutions), and were known to go as high as 8000 ppm with the higher concentrates.
And so with that in mind, it becomes quite reasonable to conclude that a continued exposure to the mucus membrane could easily lead to a systemic silver accumulation and eventually Argyria.
That said, what's also interesting about her case is where the accumulation proved so extreme that the silver compounds formed particulates in the basal layer of the skin(beneath the surface) which then remained trapped for long periods of time(years).
The sad news however is that no one appeared interested to conduct research in search for safe methods to disassociate the compounds in the skin. And what's more unfortunate, is where Miss Jacobs resorted to some of the more controversial treatments such as debridement(skin removal) which left her looking worst than she did before going in. - which is quite sad
Whatever the case may be, the fact remains that it is quite difficult to develop Argyria with today's Colloidal Silver Solutions in that would takes very large amounts for very long periods of time(+ 5 yrs) before ever reaching the point of skin discoloration. To which I'd add, if and when ever does happen, is usually so mild that it is quite easily resolved or reversed. And so, all in all, I'd say you have nothing to worry about in your case. As it pertains to topical applications and where the concentration is simply far too low to ever amount to anything.
Hope this helps
PS. I'm currently working with a individual who developed a mild case of Argyria of the hands(tops) and face. To which I'd add, has proven to be completely reversible by changing his daily CS intake from the usual ingestion method, to that of holding under the tongue and spitting afterward. To which I'd add, has proven to be every bit as effective than with the traditional intake method. While eliminating all potential for Aryria(skin discoloration) in the process.