Patch test–relevant concentrations of metal salts cause localized cytotoxicity, including apoptosis, in skin ex vivo

Yan Zhang, Niels P.J. de Graaf, Rosalien Veldhuizen, Sanne Roffel, Sander W. Spiekstra, Thomas Rustemeyer, Cees J. Kleverlaan, Albert J. Feilzer, Hetty Bontkes, Dongmei Deng, Susan Gibbs

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)


Background: Metal alloys containing contact sensitizers (nickel, palladium, titanium) are extensively used in medical devices, in particular dentistry and orthopaedic surgery. The skin patch test is used to test for metal allergy. Objective: To determine whether metal salts, when applied to freshly excised skin at patch test–relevant concentrations and using a method which mimics skin patch testing, cause in changes in the epidermis and dermis. Methods: Tissue histology, apoptosis, metabolic activity, and inflammatory cytokine release were determined for two nickel salts, two palladium salts, and four titanium salts. Results: Patch test–relevant concentrations of all metal salts caused localized cytotoxicity. This was observed as epidermis separation at the basement membrane zone, formation of vacuoles, apoptotic nuclei, decreased metabolic activity, and (pro)inflammatory cytokine release. Nickel(II) sulfate hexahydrate, nickel(II) chloride hexahydrate, titanium(IV) bis(ammonium lactato)dihydroxide, and calcium titanate were highly cytotoxic. Palladium(II) chloride, sodium tetrachloropalladate(II), titanium(IV) isopropoxide, and titanium(IV) dioxide showed mild cytotoxicity. Conclusion: The patch test in itself may be damaging to the skin of the patient being tested. These results need further verification with biopsies obtained during clinical patch testing. The future challenge is to remain above the elicitation threshold at noncytotoxic metal concentrations.

Original languageEnglish
Pages (from-to)531-542
Number of pages12
JournalContact dermatitis
Issue number5
Early online date15 Jul 2021
Publication statusPublished - Nov 2021


  • allergy
  • apoptosis
  • cytotoxicity
  • excised skin
  • nickel
  • palladium
  • patch test
  • titanium

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