A 65-year-old man had been living with well controlled Type 2 diabetes (free of complications) for over 30 years. His diabetes had been managed with diet, exercise and tablets up to 4 years previously when he was changed to twice-daily pre-mixed insulin (Human Mixtard 30 ge). After starting insulin he reported a wheal-and-flare-type reaction at the injection site every time he self-administered insulin. Approximately once in every 50 injections he would develop what he termed a 'light-up' reaction (Fig. 1) amounting to a wheal and flare at every injection site he ever used for insulin administration. These light-up reactions would often be followed by episodes of hypoglycaemia. This article is protected by copyright. All rights reserved.