Colloidal Silver: Safe and Effective? (When Not to Use)


Silver has a long history as an antimicrobial in folk medicine, with the claims that people who ate from silver dishes and cutleries were less likely to get sick. Before the advent of antibiotics, silver was widely used in medicine (1).

The History of Silver Use

While silver is still often used in medicine, many holistic health experts tout the benefits of colloidal silver as a highly beneficial cure-all. Have you ever wondered what all the hype is and is it safe and effective?

Conventional medicine recognizes the antimicrobial benefits of silver. For example, many medical device companies coat their devices with silver to prevent bacterial biofilms. Hospitals used to give silver nitrate eyedrops to newborns to prevent gonorrhea infections to the eye. Many studies show the effectiveness of silver solutions, silver gauze, or silver complexed with other antimicrobials in the hospitals to treat burn wounds. (2)

Like many folk remedies, there is not strong scientific evidence supporting some of these claims, which explains why some uses of colloidal silver are controversial.

With the rise of antibiotic resistance, silver is making a comeback as a powerful broad-spectrum antimicrobial. Colloidal silver is generally considered safe to use, but it is important to be informed about what studies say with respect to its safety and effectiveness, and whether excessive use may harm us or the environment.

What is Colloidal Silver?

In short, colloidal silver is the suspension of sub-microscopic silver nanoparticles in water. These silver nanoparticles can be anywhere from 10 – 100 nm in diameter (around 1/10,000 to 1/1,000 of a human hair) (3).

Silver nanoparticles are typically made in two different ways:

  • Physically– by grinding silver into very small particles before suspending in water as colloids.
  • Chemically– Silver salt is reduced into very small particles using a chemical reducer.

Many well-studied nanoparticles are generated with a method called “green synthesis,” which is by using a biologically-generated substance to reduce the silver salt into silver nanoparticles (4, 5).

How Does Colloidal Silver Work?

Scientist have observed that it kills germs, but they still don’t completely understand how. It is generally understood that silver nanoparticles bind to bacteria cell wall. The surface chemistry as well as the shape of the nanoparticles determine how toxic it is to the bacteria. A fraction of silver nanoparticles may react to substances in the body or the environment and become silver salt, which is an effective antimicrobial.

Although most colloidal silver is made from silver salts, they are essentially different things. Silver salts are generally a lot more toxic to bacteria and humans than colloidal silver. Silver salt solutions (e.g. silver chloride, silver oxide, silver nitrate) often react with oxygen in the air when exposed to light, resulting in precipitates. Whereas colloidal silver usually have a yellow-gold color and is stable without precipitates.

Silver salts in water have positive charge that allows it to bind up proteins, cause DNA damage, and disrupt the respiratory processes in bacteria. Silver nanoparticles may be neutral or negatively charged, depending on how it is synthesized.

In addition, silver ions are more likely to cause silver toxicity or argyria in humans than the colloidal version. However, because a fraction of colloidal silver may become silver salt, overconsumption of colloidal silver can still cause silver toxicity at very high doses.

Is Colloidal Silver Effective?

Silver is a metal and a non-essential element in the body. It is much safer to a human body than other heavy metals like lead and mercury.

This means the dose makes the poison: we can accumulate much more silver in our bodies before it becomes toxic. It is possible to accumulate too much silver in a condition called argyria or argylosis, where silver deposits in tissues and irreversibly turns the person consuming it blue. But even when the person has turned blue, the silver does not usually cause health problems in other ways.

Studies Suggest that Colloidal Silver is Effective at:

  • Killing and preventing bacterial growth, including bacteria that are antibiotic-resistant (6, 7)
  • Killing some strains of pathogenic yeasts, including Candida and Cryptococcus (8)
  • Preventing viruses from entering human cells (9)
  • Reducing inflammation in contact dermatitis (rashes from exposure to irritating chemicals) in pigs and mice (10, 11)
  • Disrupting bacterial biofilm (a slimy shield that allows bacteria to hide from antibiotics) in sheep bacterial sinusitis (12)
  • Being toxic to cancer cells (13)
  • Effectively fighting against Vibrio cholera and a dangerous strain of E. coli, both of which could cause deadly diarrhea if left untreated (14)

To date, all studies that test the effects of colloidal silver with bacteria found that it is effective, but its effectiveness is less consistent with yeasts and viruses. A comprehensive study by naturopathic doctors in Journal of Alternative and Complementary Medicine found that that it is only effective against some strains of yeasts but not others.

In addition, the same study found that colloidal silver is not effective against viruses (15). Another study tested 3 different market brands and found no effectiveness whatsoever (16).

It seems, therefore, that colloidal silver is a powerful antimicrobial, but its effectiveness can vary depending on the particular infection and quality of the product itself.

Colloidal Silver Safety

In order to understanding the safety and effectiveness of colloidal silver, it is important to have experimental data in the context of a whole animal or a whole human. Most studies are done in “in vitro,” i.e. in test tubes or in Petri dishes outside the body. With the exception of wounds, diarrhea, and dermatitis, we have only observed the effectiveness of colloidal silver against germs on Petri dishes or on human cells that are grown on Petri dishes, which are not enough to show that they are effective.

A human body is a lot more complex than a Petri dish, so simply because something kills germs on a Petri Dish doesn’t mean we should eat it to prevent or treat an infection. We still need to understand how silver affects the rest of the body, and whether it can even travel to where we need it most if we take it internally. Therefore, more studies are needed to understand how it works in our bodies (in vivo).

When we ingest colloidal silver, our small intestines can absorb around 10 – 18% of silver nanoparticles into the bloodstream, while remaining silver nanoparticles pass through our gut. In our bloodstream, the nanoparticles then bind to a protein in our blood called albumin as it gets carried around the body. Typically silver proteins are a lot less effective against germs than silver alone, which raises the question of whether colloidal silver is effective outside of the gut when taken internally. (17)

An Alternative To Antibiotics?

Colloidal silver might seem like a promising option over antibiotics, but it still has some of the side effects of antibiotics. For this reason, I’ve always exercised caution and not over-used it, as evidence shows it may be harmful if used regularly or over a long period of time.

Gut Damage and Bacterial Resistance

Recently, two studies independently examined the gut microbiota of mice and rats fed with colloidal silver, and both found that it did indeed disrupt the gut flora (18, 19). Another study that examined the digestive tissue after ingestion of colloidal silver also found that it can damage the gut cells (20).

While bacterial resistance to silver salt has been long known (21), one study showed that bacteria can become resistant to colloidal silver after many generations of exposure (22).

Environmental Concerns

With its broad-spectrum antimicrobial, silver nanoparticles and silver salts present some environmental concerns. Currently, silver nanoparticles are present in the environment at the concentrations that are about one in a thousandth times the dose that would be toxic to fish and other marine animals (23).

Presently, silver nanoparticles are present in sewage sludge that are used in landfill rather than dumped into the sea, so this also presents a risk of it getting reabsorbed back into our food supply. While we understand that colloidal silver affects our gut bacteria, we still don’t completely know how it affects the health of bacteria, yeasts, and other microorganisms in the environment. We do know that the health of our soil is closely linked to the health of our gut, so we want to be careful about disrupting it.

Uses for Colloidal Silver

Studies have shown that silver is effective in treating and preventing infections when applied externally to wounds and when used as a sinus rinse. In addition, it may be effective in treatments of acute diarrhea. Therefore, colloidal silver can be safe and effective when used externally, or when targeting pathogens in the gut.

Because colloidal silver does have some side effects, research suggests using it carefully rather than liberally. In addition, because it can interfere with or enhance the effects or side effects of some medications, always consult your physician before using it in conjunction with any medications.

Colloidal silver is marketed as a dietary supplement and is relatively unregulated. The manufacturer is responsible for the safety and effectiveness of these products. It is concerning that a random test of colloidal silvers on the market often found ones that are ineffective or even contaminated with bacteria (24).

If you choose to use colloidal silver, be sure to purchase them from a reputable brand. There many available, but this is the brand I keep on hand for external use and as a sinus rinse.

What’s your experience with colloidal silver? Please share in the comments below.


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