Colloidal silver illustrates many of the classic characteristics of quack alternative medicines. It has a history of mainstream use based on tradition and theory, but it was abandoned by science-based medicine in favor of safer and more effective treatments. There are a few legitimate uses of silver-containing compounds, and these are misrepresented as supporting inappropriate uses of these and other silver-containing substances. There is some laboratory research that shows biologic effects of silver in test tubes, and this too is misused to justify giving silver products to sick patients. There is virtually no research on colloidal silver in actual patient, and what there is fails to meet basic standards of quality. There are, however, lots of anecdotes which people wrongly believe can be used to support treatment with this snake oil.
Colloidal silver is a liquid, usually water, with microscopic particles of silver suspended in it. While some medical uses of silver are legitimate, none involve oral colloidal silver. Topical use of ointments for burns and to prevent eye infections in newborns, and impregnation of catheters and other medical equipment with silver, do have some benefits. However, taking colloidal silver orally is an entirely different thing, and there are no proven benefits from this practice. There are, however, significant risks.
I haven’t previously covered this topic because the risks and lack of benefits from colloidal silver have been thoroughly covered elsewhere, and fortunately it is not at the top of the list for alternative treatments of pets. However, a reader recently drew my attention to a “study” of colloidal silver in dogs. As poorly conducted and unreliable as this paper is, undoubtedly some will claim it as evidence supporting the use of colloidal silver in dogs, so I felt it was worth discussing why it is not.
First, though, here are a few sources discussing the lack of benefits and the real risks of colloidal silver in humans:
There are no high quality studies on the health effects of taking colloidal silver, but we do have good evidence of its dangers.
Silver has no known function or benefits in the body when taken by mouth.
Silver is not a nutritionally essential mineral or a useful dietary supplement.
There are no legally marketed prescription or over-the-counter drugs containing colloidal silver that are taken by mouth.
National Center for Complementary and Integrative Health
All over-the-counter (OTC) drug products containing colloidal silver ingredients or silver for internal or external use are not generally recognized as safe and effective and are misbranded. FDA is issuing this final rule because many OTC drug products containing colloidal silver ingredients or silver salts are being marketed for numerous serious disease conditions and FDA is not aware of any substantial scientific evidence that supports the use of OTC colloidal silver ingredients or silver salts for these disease conditions.
Food and Drug Administration
Colloidal silver isn’t considered safe or effective for any of the health claims manufacturers make. Silver has no known purpose in the body. Nor is it an essential mineral, as some sellers of silver products claim.
There is no data to support silver to treat infections.
So for what diseases is there evidence for which colloidal silver is efficacious? Well, nothing. Pubmed is silent on taking colloidal silver to benefit any disease, infection or otherwise. There are no clinical trials to show efficacy. Nothing.
When taken orally, silver can interact with and reduce the effectiveness of tetracycline, quinolone, and penicillamine. Long term use can cause silver deposition in the skin and mucous membranes leading to an irreversible condition called argyria, characterized by bluish-gray to gray-black pigmentation. Other adverse effects include seizures (6) and kidney damage. Pregnant women should not consume colloidal silver as it can cause developmental abnormalities in the fetus.
Memorial Sloan-Kettering Cancer Center
Colloidal silver can cause serious side effects. The most common is argyria, a bluish-gray discoloration of the skin, which is usually permanent.
Colloidal silver can also cause poor absorption of some drugs, such as certain antibiotics and thyroxine (used to treat thyroid deficiency).
National Center for Complementary and Integrative Health
Brain and nerve damage from silver exposure is rare, but colloidal silver can cause kidney damage, stomach distress, and headaches.
The most common problem associated with silver exposure is argyria: The skin turns a bluish gray as granules of silver accumulate in the body.
Harvard Medical School
So we have a product with no proven benefits, only anecdotal claims and inappropriate extrapolation from lab studies. We also have proven significant risks. Seems like a pretty clear case for abandoning the treatment, as science-based medicine has done. Unfortunately. It is still easy to find alternative practitioners recommending colloidal silver, for veterinary patients as well as for people.
A Veterinary “Study” of Colloidal Silver
These practitioners may be tempted to claim validation from a paper published last year. This “study” failed to meet even the most basic standards of clinical research, which is probably why it was published in a nanotechnology journal rather than a medical journal. It is effectively a collection of anecdotes dressed in the trappings of scientific research, and it does not justify using colloidal silver in dogs.
Bogdanchikova N. Vázquez-Muñoz R. Huerta-Saquero A. et al. Silver nanoparticles composition for treatment of distemper in dogs. International Journal of Nanotechnology. 2016;13(1-3):227-237.
The paper reports a comparison of dogs with canine distemper, a viral infection, treated with colloidal silver or with standard medical treatment for this disease. It purports to show that silver improved the survival of dogs with distemper as long as they did not have neurologic symptoms. Dogs without such symptoms who were treated with silver appeared to be more likely to survive the disease than dogs without neurologic signs who received standard care. The authors then confidently claim silver was effective in treating dogs with distemper as long as they did not have the neurologic form of the disease.
It would be fantastic if this were true since standard care is not very effective for many dogs with canine distemper. Unfortunately, there are very many reasons why this study cannot, in fact, support the claims the authors have made for colloidal silver. To explain this, I will briefly review how scientific research is supposed to be different from mere anecdote, and why this paper doesn’t meet the basic criteria for reliable research.
I’ve discussed at length previously why stories, sometimes called anecdotal evidence, are not reliable for judging the safety of effectiveness of medical treatments or the causes of disease. Scientific research, while still imperfect, does a better job because it has methods built into it which compensate for common flaws and limitations in human observation and judgment. In clinical trials designed to test medical treatments, these methods include:
Randomization of patients– When comparing two groups, one of which gets a treatment and one which does not, the patients in the groups must be as similar as possible in every way except for the treatment, Otherwise, differences between them might be due to something other than the treatment being tested. Assigning patients to groups randomly, that is by chance, helps ensure the groups are comparable. Any way of assigning patients that is not completely left to chance introduces bias into the study.
Blinding to randomization– Since all our choices and decisions are unconsciously, if not consciously, biased by our existing beliefs, if we are aware of who gets assigned to the test treatment or the comparison group, we can influence this in a way that defeats the purpose of randomization. For this reason, clinical trials require that people involved in the trial don’t know which group any patient is assigned to (they are “blinded” in the language of medical research).
Blinding to treatment– Just as people in the study shouldn’t know which group patients are assigned to, they also shouldn’t know which treatment people are getting. Anyone treating or evaluating patients who knows which group they are in will inevitably unconsciously skew their actions and the results in favor of the outcome they expect or hope for.
Statistical comparisons– Various kinds of mathematical tests are used to compare differences between groups to help identify how likely those differences are to be due to chance rather than the treatment. These methods have many flaws and limitations, but they help make research results more reliable than simple observation.
The paper which claims to report a research study comparing dogs with canine distemper infections treated with colloidal silver and those treated with standard medical care does not meet even these basic criteria for a controlled clinical trial. It looks like a scientific study, but without these controls for bias, it is simply a collection of anecdotes.
To begin with, dogs were assigned to colloidal silver treatment or standard care based on whether or not their owners were offered silver treatment and agreed to allow it. There is nothing random about this. The doctors and the owners simply decided who would get the experimental treatment and who wouldn’t, which guarantees the patients will differ in ways likely to affect the outcome. If, for example, owners of sicker dogs were afraid to try an experimental treatment while owners whose dogs were not as ill were more willing to accept it, then dogs in the control group would automatically be sicker, and have worse outcomes, than dogs in the treatment group. This is just one of many ways in which the lack of randomization or blinding to randomization could influence the results of this study.
There is also no indication that owners, caregivers, or research personnel were blinded to which group patients were part of. If this is true, the lack of this most basic control for bias means the people involved in the study could have intentionally or unconsciously influence the results in many ways.
There were certainly no statistical comparisons made in the paper. It is possible that even the authors recognized that the lack of standard methods for controlling bias and error in the study made any such mathematical comparison inappropriate and meaningless. However, it may also be that they felt the results were so clear and obvious that statistical comparisons were unnecessary. In either case, the lack of these comparisons further reduces the reliability of the results.
There are a number of other serious problems with this paper, some of which have to do with the nature of canine distemper infection and how it is diagnosed and treated. Canine distemper virus (CDV) affects different dogs differently. Many do not develop serious illness at all. Puppies get sicker than older dogs, and dogs with other diseases or poor immune system function are more likely to get seriously ill or die than healthier dogs. Different strains of the virus also produce different degrees of illness. All of these variations mean that the course of illness and chances of survival vary greatly between dogs. This is exactly the kind of variation that requires randomization and blinding to randomization to ensure that study subjects getting different treatments are truly comparable. Without these controls, it is quite likely that dogs getting silver treatment were different in relevant ways from dogs not getting silver, and any differences in survival could easily be due to these other differences.
It is even possible that some of the dogs in this study did not have CDV at all. There are other diseases that can similar to those of CDV, especially when there is no neurologic involvement. symptoms. The more typical symptoms a dog has, and the more consistent their physical exam findings and lab tests are with CDV, the more likely they are to have the disease. Dogs with respiratory and gastrointestinal signs who do not have neurologic disease may actually have other causes of illness, not CDV.
These are precisely the dogs in this study who appeared to recover with silver treatment. While the authors did test for antibodies to CDV, these can also be found in dogs with CDV who are sick for other reasons and in dogs who have been recently vaccinated for CDV. Very few other clinical findings or lab tests were reported to support the diagnosis. The design of this study, therefore, does not allow us to say with any certainty that the dogs who fared better did so because of the treatment. It is also possible they may not have had as severe a form of the disease as the dogs who died, or that they didn’t have CDV at all.
The death rate for CDV is also highly variable. Studies have suggested from 50-80% of dogs with distemper will die. However, most animals with mild symptoms will recover, adults are much less likely to die than puppies, and dogs with neurologic signs have a higher mortality rate than those without. Therefore, comparisons of mortality between groups treated differently must account for these differences, which was not done in this study.
As an example, while dogs without neurologic signs were similar in average age between the two groups (19 months for the silver group and 14 months for standard treatment), the ages of dogs in these groups with neurologic symptoms were very different (14 months on average for the silver group and 40 months for the standard treatment). Age is one factor that influences the likelihood of CDV and the mortality rate, so such differences can influence differences in outcomes regardless of the treatment given.
As mentioned before, dogs were assigned to standard treatment or silver based on the choices of owners and investigators. It is likely the severity of illness would differ between groups when patients are assigned in this way. Also, the type of treatment within the silver group varied, with sicker animals getting treatment more often and during a different period of time. This further complicates any attempt to compare groups.
Mortality rates differed between the treatment groups, which is the main basis for the claim that the colloidal silver had some effect. However, given the failure to ensure the groups were truly comparable, these differences can’t be used to determine if there is any effect from the treatment. All but one of the dogs with neurologic symptoms died regardless of treatment. All of the dogs with other symptoms also died with standard care, while all of the dogs with non-neurologic signs survived in the silver group. This would be a dramatic difference if it were seen in a study with appropriate methods and more than the 9 animals in the treatment group. With these limitations, unfortunately, this apparent difference is meaningless, a mere anecdote rather than a true scientific comparison.
Colloidal silver has been abandoned as a medical treatment by mainstream medicine because there is no reason to believe it works and it is clear it has significant risks. While silver has some effect on infectious disease organisms in test tube studies, so do bleach and gamma radiation. This doesn’t mean any of them are appropriate as treatments for infection in living patients. There is no good clinical research evidence to justify using colloidal silver in humans or veterinary species. The research that is available, such as the study of colloidal silver in dogs with presumed canine distemper, is inadequate to draw conclusions and amounts to anecdotes made to look like scientific research.