Jumping into the fray :) .... I decided to go do some literature searches
on the MEDLINE database to see what I could find about the use of colloidal
silver.  The first thing I noticed is that there really is very little out
there on the use of colloidal silver, and I couldn't find any papers
detailing any sort of clinical research on its use.  I've listed below what
I did find and tried to give a brief summary of each item.  Anyone living
near a university, particularly one with a vet or med school, should be
able to find these articles.  If you can't find them, ask the library to
get them on interlibrary loan (takes 1-2 weeks).  I had to do that for a
couple of them myself because our med school libraries didn't have a
particular journal, or had cancelled a subscription.
 
1.  Antibacterial Efficacy of a Colloidal Silver Complex, Brentano, L.,
Margraf, H., Monafo, W.W., and Moyer, C.A.  Surgical Forum 17: 76-78, 1966.
 
In order to determine the best agent for antibacterial use on wound
dressings for burns, the authors tested silver nitrate, colloidal silver
("Collargol Rx" - no specifics given), and a mixture of silver nitrate and
Collargol.  They tested these three agents against three strains of
bacteria, under three different growth conditions.  In all cases they found
that colloidal silver alone was relatively ineffective, as compared to
either the silver nitrate alone, or the mixture, requiring up to a 40-fold
higher concentration to attain the same effect.
 
2.  Antimicrobial Activity and Action of Silver, Russell, A.D., and Hugo,
W.B.  Progress in Medicinal Chemistry 31:351-370, 1994.
 
This is a rather long paper which goes into the historical aspects of
silver use, the properties and uses of silver compounds, the mechanisms of
antimicrobial action, and bacterial resistance to silver.  Obviously I
can't summarize the whole thing here but there are some interesting points.
Pure silver is inactive, however surface-oxidized or tarnished silver has
the antimicrobial effect.  In general the antimicrobial action of silver is
decreased in the presence of proteins, phosphates, chlorides, sulphides,
and hard water.  Argyria can occur as a result of prolonged silver therapy,
one example being noted of a 59 year old patient undergoing silver
sulfadiazine therapy for venous leg ulcers.  Bacterial resistance to silver
can be either acquired or innate.  This paper does not focus on any one
silver compound and does not mention colloidal silver much at all.  It is
however, a very good overview and would be interesting reading, especially
for anyone with a background in chemistry or biochemistry.
 
3. Silver Products for Medical Indications: Risk-Benefit Analysis, Fung,
M.C., and Bowen, D.L.  Journal of Toxicology - Clinical Toxicology,
34(1):119-126, 1996.
 
This paper goes somewhat into the history of silver use and its physical
and chemical properties.  It also mentions the dose considered as safe
exposure by the EPA, called the Reference Dose (Rfd), which is an estimate
of daily exposure that is not likely to be associated with deleterious
effects during a person's lifetime.  The Rfd for oral silver exposure is
5ug/kg/d, which translates to 350ug/d for a 70 kg adult.  They have a
table listing OTC as well as prescription silver products.  Seven cases of
argyria are noted, in which people were self-treating with various silver
products.  In their conclusion, they "emphasize the lack of established
effectiveness and potential toxicity of these products."
 
Based on what I've read, and what I haven't read (IOW, I haven't seen any
peer-reviewed papers which say that colloidal silver is safe and
effective), I won't be using it on myself or my ferrets.  While certain
silver compounds have been used successfully for external treatments, I
can't see that it would be any more useful internally than antibiotics,
which are targeted to certain bacteria, rather than having a general effect
(silver cannot distinguish between good and bad bugs).  Added to that the
potential for toxicity, and I don't feel the risk is justified.  If anyone
does decide to use it, just be aware of the potential pitfalls.  Silver is
not a magic bullet.
 
Karen
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A righteous man has regard for the life of his beast, but the mercy of
the wicked is cruel."
                                         (Proverbs 12:10 RSV)
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If you love ferrets, check out:
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[Posted in FML issue 2587]