I used this sunscreen a while back, liked it and was considering repurchasing. I was interested to see another user's comment that the silver used as a preservative in the product could be dangerous. Concerned,I did as she recommended and did a search on PubMed. All the articles I found on the subject indicated that use of silver as a preservative in cosmetics doesn't pose a danger.
A summary of two of the articles is copied below:
Nanomedicine. 2010 Aug;6(4):570-4. Epub 2010 Jan 7.
Silver nanoparticles as a safe preservative for use in cosmetics.
Kokura S, Handa O, Takagi T, Ishikawa T, Naito Y, Yoshikawa T.
Molecular Gastroenterology and Hepatology, Kyoto Prefectural University of Medicine, Kyoto, Japan. firstname.lastname@example.org
Concern is continuously raised regarding the safety of preservatives, which are crucial in most cosmetic preparations. The antimicrobial effects of silver (Ag) are well recognized; however, Ag has some limitations as a preservative, such as its interference with salts. In this study, we investigated the effects of recently synthesized Ag nanoparticles on microorganisms, the permeability of Ag nanoparticles in human skin, and the cytotoxicity of Ag nanoparticles in human keratinocytes under ultraviolet B irradiation. Ag nanoparticles were found to be very stable, and they did not exhibit sedimentation for over 1 year. Ag nanoparticles showed sufficient preservation efficacy against mixed bacteria and mixed fungi, and did not penetrate normal human skin. At concentrations of 0.002-0.02 parts per million, Ag nanoparticles had no effect on HaCaT keratinocytes and did not enhance ultraviolet B-induced cell death. These results suggest that Ag nanoparticles may have potential for use as a preservative in cosmetics. From the clinical editor: In this study, the effects of recently synthesized Ag nanoparticles were investigated on microorganisms, along with the skin permeability and the cytotoxicity in human keratinocytes under UVB-irradiation. Ag nanoparticles were found to be very stable, showed sufficient preservation efficacy against mixed bacteria and mixed fungi, and did not penetrate normal human skin. Ag nanoparticles appear to be suitable for use as a preservative in cosmetics.
2010 Elsevier Inc. All rights reserved.
Int J Cosmet Sci. 1997 Feb;19(1):27-36.
Utilization of electrochemical silver ions as preservative agent in cosmetic dispersions.
Scalzo M, Cerretou F, Orlandi C, Simonetti N.
Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Facolta` di Farmacia, Universita` `La Sapienza', P. Le Aldo Moro 5 00185 Roma Italy.
The use of anodic silver ions as preserving agents in cosmetics was tested by a challenge test in a set of cosmetic dispersions with the addition of known preservative inhibitors or micro-organism growth-promoters such as humectants, hydrosoluble collagen and vegetable extracts. Silver's microbicidal efficacy, compared to that of imidazolidinyl urea or methyl p-hydroxybenzoate, showed a more efficient activity especially in the presence of proteinaceous material. This agent may represent a good and safe protection for finished products both in manufacture and during use.