Abstract
Herein, we present the case of a 45-year-old woman with a history of Graves' disease who underwent radioactive iodine therapy and was prescribed different oral preparations of thyroxine. Despite initial tolerance to the medication, she developed hypersensitivity reactions 3 months after consumption, which presented as urticarial rashes, erythematous maculopapular eruptions and angio-oedema. She tried a different preparation of thyroxine accompanied by antihistamines but continued having persistent reactions. This led to her discontinuation of thyroxine, resulting in overt hypothyroidism with secondary dyslipidaemia and weight gain. A diagnosis of delayed thyroxine hypersensitivity was made based on history, clinical assessment and supportive evidence from the Naranjo Adverse Drug Reaction Probability Scale.