Cobalt nanoparticles cause allergic contact dermatitis in humans

Area of Science:

• Dermatology
• Toxicology
• Nanotechnology

Background:

• Cobalt (Co) is a known cause of allergic contact dermatitis (ACD).
• The increasing use of cobalt nanoparticles (CoNPs) necessitates understanding their potential to induce ACD in individuals already sensitized to cobalt.

Purpose of the Study:

• To determine the extent to which CoNPs elicit ACD responses in individuals with existing cobalt contact allergy.
• To compare the immune response induced by CoNPs with that of cobalt chloride (CoCl2) in skin reactions.

Main Methods:

• Patch testing was performed on 14 individuals with cobalt allergy using CoNPs, CoCl2, a cobalt-containing hard-metal disc (positive control), and a negative control.
• Clinical allergic responses were assessed by a dermatologist at Days 2, 4, and 7.
• Skin biopsies and wipe samples were collected for analysis of cobalt levels (ICP-MS), gene expression (qRT-PCR), and histopathology.

Main Results:

• Patch testing with CoNPs induced allergic reactions in cobalt-sensitized individuals.
• Frequencies of positive patch-test reactions were significantly lower for CoNPs compared to CoCl2 or the positive control at all timepoints.
• CoNPs induced immune responses comparable to CoCl2, with lower cobalt skin doses observed for CoNPs.

Conclusions:

• Cobalt nanoparticles (CoNPs) are potent elicitors of immune responses in cobalt-sensitized individuals.
• Despite lower skin doses, CoNPs demonstrated identical immunological profiles to cobalt chloride.
• Further investigation is required to fully ascertain the potential health risks associated with CoNPs.