Safety profile of cobalamin in patients with contact sensitisation to cobalt

Cobalt is a well-known hapten involved in allergic contact dermatitis. In individuals sensitized to this transition metal, administration of vitamin B12 (cobalamin) preparations can provoke hypersensitivity reactions due to the cobalt ion within the cobalamin structure. Although the prevalence of cobalt allergy is low, affecting approximately 1-3% of the general population, caution is warranted when prescribing vitamin B12 formulations to these patients. Regulatory authorities in several countries have issued specific warnings to healthcare professionals and patients about the risk of hypersensitivity reactions to hydroxocobalamin and cyanocobalamin in cobalt-sensitized individuals. This cross-reactivity may impede effective vitamin B12 supplementation, potentially leading to delayed diagnosis or suboptimal treatment outcomes. This article outlines management strategies to support appropriate vitamin B12 therapy in patients with cobalt sensitization.