What is Silver Dihydrogen Citrate?

This is part of our ongoing series helping consumers better understand chemicals, chemistry, and product formulations. We translate the science, bust the myths, and give you an honest assessment, so you can make informed choices for your family!

Ingredient:

Silver Dihydrogen Citrate (SDC)

What it is:

Ionic silver in a citric acid solution.

What it does:

Fights bacteria. Most personal care products are made with a lot of water and a variety of nutrients which make an incredibly hospitable breeding ground for microorganisms. What’s worse – the product might smell and look just fine, but be swarming with bacteria or fungi that are dangerous to your health. Effective preservatives are vital for ensuring safety!

Why we use it:

Preservatives are especially difficult to formulate because they have to be strong enough to kill bacteria, but they also can’t impact the effectiveness of other ingredients. Of course, for The Honest Company, safety is key. Conventional preservatives like parabens are linked to hormone disruption (1-6). Another common category of conventional preservatives are formaldehyde-releasers, but formaldehyde is a known carcinogen (7,8). We were thrilled to discover SDC which is non-toxic to you and your family, non-irritating, colorless, and odorless.

  • In a scientific review conducted by the EU’s Scientific Committee on Consumer Products, they deemed SDC to be non-toxic by oral exposure, non-toxic by dermal exposure, non-irritating, and that it’s not a skin sensitizer.
  • The World Health Organization assessed the safety of using silver compounds for sanitizing drinking water and concluded that there have been no reports of toxic effects resulting from the exposure of healthy persons to these compounds.

Safe and effective – that’s what we like!

References:

  1. Byford JR, Shaw LE, Drew MGB, Pope GS, Sauer MJ, Darbre PD (2002). Oestrogenic activity of parabens in MCF7 human breast cancer cells. Journal of Steroid Biochemistry & Molecular Biology 80:49-60.
  2. Darbre PD, Aljarrah A, Miller WR, Coldham NG, Sauer MJ, Pope GS (2004). Concentrations of parabens in human breast tumours. Journal of Applied Toxicology 24:5-13.
  3. Darbre, P. D., & Harvey, P. W. (2008). Paraben esters: review of recent studies of endocrine toxicity, absorption, esterase and human exposure, and discussion of potential human health risks. Journal of applied toxicology, 28(5), 561-578.
  4. Marques-Pinto, A., & Carvalho, D. (2013). Human infertility: are endocrine disruptors to blame?. Endocrine connections, 2(3), R15-R29.
  5. Boberg, J., Taxvig, C., Christiansen, S., & Hass, U. (2010). Possible endocrine disrupting effects of parabens and their metabolites. Reproductive Toxicology,30(2), 301-312.
  6. Shaw, J. (2009). Estrogenicity of parabens revisited: Impact of parabens on early pregnancy and an uterotrophic assay in mice. Reproductive toxicology,28(1), 26-31.
  7. Formaldehyde and Cancer Risk. (n.d.). Retrieved January 05, 2015, from http://www.cancer.gov/cancertopics/factsheet/Risk/formaldehyde
  8. Swenberg, J. A., Moeller, B. C., Lu, K., Rager, J. E., Fry, R. C., & Starr, T. B. (2012). Formaldehyde Carcinogenicity Research 30 Years and Counting for Mode of Action, Epidemiology, and Cancer Risk Assessment. Toxicologic pathology, 0192623312466459.
  9. Chapman, J. S. (1998). Characterizing bacterial resistance to preservatives and disinfectants. International Biodeterioration & Biodegradation, 41(3), 241-245.
  10. Chapman, J. S., Diehl, M. A., & Fearnside, K. B. (1998). Preservative tolerance and resistance. International journal of cosmetic science, 20(1), 31-39.

This post was revised as of 1/26/2016.

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  • Peter Benedict

    I got to think this is the way to go. Good water doesn’t need any preservation, thank goodness.

  • Lori

    Could it kill good bacteria like how oral antibiotics do?

  • Shari

    I’ve been meaning to write on this blog for a while now, as I contacted the manufacturer of silver dihydrogen citrate with a concern over a year ago and never heard back from them. It is a relatively new ingredient in products and sounds fabulous, miraculous even, however I am worried about those who do not flush heavy metals easily. Is it possible that this product gets absorbed by placing this product on sensitive skin (such as baby bottoms/even mucous membranes) and if so, is this safe? I am a mom of three kids under four years and I am very mindful of what I place on and in their bodies because they do not flush toxins as readily as other individuals. I had heavy metal poisoning from a silver nitrate procedure (standard medical practice), so I am concerned about using any product known to contain heavy metals. How is this safer and different from other silver based compounds, such as silver nitrate?

  • A. L.

    How is this a natural ingredient??

    If I’m supposed to be okay with chemicals in my baby products why use Honest products at all? You say this is safe because science has shown it to be safe, but has science shown that the other ingredients are safe? Are we supposed to believe that everything “natural” is safe and everything “synthetic” is toxic, or are we supposed to evaluate safety based on scientific testing of ingredients regardless of origin? You seem to want to have it both ways. Maybe change your name to “Hypocritical Company”?

  • Rebekah Osorio

    I think the interview below regarding the silver citrate will be interesting to you all. A nurse from the manufacturing company discusses how silver citrate is processed in the body further on in the interview.

    http://www.naturalingredient.org/Articles/mulhaupt.html

    In defense of Honest, preserving products so they are safe for use is EXTREMELY critical. There aren’t a lot of natural preservatives that actually work for solid, broad spectrum uses that take care of all pathogens.

    This silver citrate may technically not be “natural,” and it can be used effectively at EXTREMELY small amounts (0.01% of the total formula), unlike many other preservatives that need 1-4%. Even colloidal silver must be consumed regularly in huge doses before it will cause argyria, and silver citrate is NOT the same chemically as colloidal silver.

    If it becomes inert when absorbed into the body and is processed out by the kidneys like the interviewee states, and yet it still acts as an effective preservative that will PROTECT you and your children from serious contamination (when other natural preservatives very well may not), that is a SERIOUS win for us all.

  • S.Z.

    I understand that most cosmetic products need some kind of preservatives to last longer. However, researches have come up to show that Silver ion can disrupt ecological balance when present in water. And when ingested, it can also disrupt gut microbial balance, which is essential for anyone’s overall healthiness. Also some researches have shown that bacteria actually can develop resistance against Silver ion. Especially this is a baby product which can alter their gut microbial and affect them life long. If it’s claimed only for external use, that’s OK. But it’s also claiming for cleaning pacifiers…This is a big NO NO to me…Putting up some citations may make you look “honest”. However, these citations are mostly about how bad the other preservatives are. Where are the recent citations about using Silver ion as preservative and killing bacteria?

  • Kathleen O’Laughlin

    I have been reading what I can get my hands on about silver dihydrogen citrate because I have used it in my lotions made with goat’s milk and it works well. My concern is how ecologically safe is it? I am finding conflicting claims about how it can affect fish. Does anyone know of any credible sources to find out more?