Conclusion
We reported the case as first presenting hyperpigmented macules and patches on the face, neck and upper back after vitamin B12 ingestion. The results of the patch test with the cobalt also showed hyperpigmented reactions consistent with the clinical presentation suggesting the diagnosis of systemic pigmented contact dermatitis resulting from oral administration of cobalamin. The diagnosis was confirmed by histopathological results of the positive patch test results corresponding to the previous active lesions. We suggest investigating systemic pigmented contact dermatitis in reaction to cobalt when patients present unexplained hyperpigmented lesions.