A suspension of silver particles or silver ions in water, sold as a supplement and marketed for infections and immune function. Silver has no known physiological role in the human body and no dietary requirement.
Colloidal silver is included here because it is sold alongside minerals and because the case against it is unusually complete. Silver is not an essential nutrient — no human enzyme or process requires it. The FDA ruled in 1999 that over-the-counter colloidal silver products are neither generally recognised as safe nor effective for any condition, and both the FDA and FTC have taken repeated action against sellers making disease claims. There are no controlled trials showing benefit from ingesting it. What there is, well documented, is argyria: permanent blue-grey discolouration of skin and mucous membranes from silver deposition, which does not resolve after stopping and has no effective remedy. Topical silver dressings in wound care are a separate, legitimate medical use and are not the same product.
Regulation: The FDA issued a final rule in 1999 stating that over-the-counter drug products containing colloidal silver or silver salts are not generally recognised as safe and effective, and has issued warning letters to sellers. The FTC has acted against health claims. No Tolerable Upper Intake Level exists because silver has no established nutritional role; the EPA has set an oral reference dose based on argyria risk.
What the research used
The amounts, forms and durations published trials of Colloidal silver actually administered.
These are the amounts published trials administered — not a recommendation, and not a dose to copy. Trial participants were screened, supervised and given a characterised preparation. What is in a retail bottle is frequently not what was studied, and the amount that suits one person is not general advice.
Studied for Any use
0 µg
Not enough
No safe or effective dose has been established for ingested silver, because there is no requirement to meet and no demonstrated benefit to target. The EPA reference dose, derived from argyria case data, corresponds to a small fraction of what many products deliver in a daily serving.
This is general information about food, not medical advice. It cannot diagnose, treat or replace guidance from a clinician who knows your history.
When it was taken
Each window says whether a trial compared it against an alternative, or whether it is convention and pharmacology. Most timing advice is the second kind.
None of the timings below were directly compared in a trial. They reflect how the research happened to dose, or what the pharmacology implies — which is not the same as a timing being better.
🕐Any time
Not enough
No timing has been studied, because no benefit has been demonstrated to time.
Timing was not directly compared. This reflects convention or how the compound behaves in the body, not a trial showing this window works better.
The evidence in depth
Best supported: Not enough
What each association actually rests on, and the papers behind it. A rating describes the state of the research, not how promising the supplement sounds. How we rate evidence.
There is no controlled human evidence that ingesting colloidal silver affects infection or immune function. Silver ions are antimicrobial on surfaces and in wound dressings, which is a topical application at concentrations that have nothing to do with what happens after swallowing a dilute suspension. Regulators have concluded these products are not recognised as effective for any condition.
Not enough evidence. Not enough human research to say anything useful yet.
Systematic review · Expert reviews in molecular medicine · 2023 · PMID 37534437
Deep research mode adds each paper’s own conclusion and stated limitations.
Things to know
Interactions, contraindications and dose limits, most serious first. Concentrated extracts interact with medication in ways the whole plant does not, so this section carries more weight here than it does on a food page.
Too much
Argyria — permanent blue-grey skin discolouration
Silver deposits in skin, nails, gums and internal organs, producing an irreversible slate-blue or grey discolouration that intensifies with sun exposure. It does not resolve after stopping, laser treatment is only partly effective, and multiple well-documented cases have followed ordinary use of commercial products.
Worth knowing
No established benefit, and regulators have said so
The FDA concluded in 1999 that these products are not generally recognised as safe or effective, and enforcement actions have continued since — including against sellers promoting silver for serious infectious diseases. Using it in place of effective therapy for an actual infection is the substantive risk.
Too much
Neurological and organ effects at high exposure
Beyond argyria, case reports describe seizures and kidney damage after heavy colloidal silver ingestion, and silver accumulates in the liver, kidneys and nervous system. Silver nasal sprays additionally risk local damage and loss of smell.
Interaction
Reduces absorption of antibiotics and thyroid medication
Silver reduces the absorption of tetracyclines, fluoroquinolones and penicillamine, and has been reported to interfere with levothyroxine. Given that the product is often taken during infections, the antibiotic interaction is not hypothetical.