Metals with known sensitizing potential as ingredients in oral care products

Wanesa Wolowiec1, Radoslaw Spiewak2

1. Cosmetology Graduate, Jagiellonian University Medical College, Krakow, Poland
2. Institute of Dermatology, Krakow, Poland

Source: Wolowiec W, Spiewak R. Metals with known sensitizing potential as ingredients in oral care products. Contact Dermatitis 2026; 94 (Supplement S1: Congress of the European Society of Contact Dermatitis [ESCD], 24-27 June 2026, Copenhagen, Denmark): 17.

Purpose: Repeated use of oral care products may create conditions conducive to the development of contact allergy. Toothpaste ingredient lists include various metal compounds that have been reported to cause allergic reactions. Oral exposure to metals could result in local allergic reactions, e.g., cheilitis or stomatitis, they also could provoke systemic reactivation of ACD. Nevertheless, tolerogenic effects of oral exposure also are possible. Depending on the compound, the bioavailability of particular metal, e.g., releasing free ions via dissociation or metabolic decomposition, may greatly vary which may determine the response.

The aim of this study was to create an inventory of these metal compounds.

Methods: Photos were taken of the ingredients listed on the packaging of products available in stores in Krakow between 15 and 27 January 2026. The photos were scanned, and the ingredients were compiled and analysed.

Results: Altogether 75 toothpastes and 45 mouthwashes were identified, 87% of international and 13% of domestic brands. Various compounds of metals with known sensitizing potential declared in the toothpastes included compounds of copper (19 toothpastes), titanium (10), tin (7), zinc (7), aluminum (6), iron (3) and strontium (2). Copper occurred as an adduct of insoluble pigments copper phthalocyanine (CI 74160; 13) and phthalocyanine green G (CI 74260; 6), titanium as dioxide (CI 77891; 10), tin as soluble stannous fluoride (6) and insoluble tin oxide (CI 77861; 1), zinc as gluconate (4), citrate (2) and chloride (1), aluminum as lactate (5) and silicate (1), iron as oxides CI 77491, CI 77492, CI 77499 (1 each), whereas strontium as soluble acetate (2). The metal compounds of interest were not listed in 42 (56.0%) toothpastes and 43 (95.6%) mouthwashes. Zinc citrate and zinc sulfate were each present in one mouthwash.

Conclusions: Compounds of potentially sensitizing metals are frequent in toothpastes but not in mouthwashes.

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Document created: 29 June 2026, last updated: 7 August 2026.