Porphyria is a group of inherited disorders of haem biosynthesis, in which enzyme defects in the pathway that builds haem cause accumulation of porphyrin precursors. The two main patterns are acute porphyrias, with attacks of severe abdominal pain, neuropathy, and psychiatric symptoms triggered by drugs, alcohol, fasting, or hormonal changes, and cutaneous porphyrias, with blistering photosensitivity. Nutrition plays a direct therapeutic role: carbohydrate loading can abort acute attacks by repressing the pathway’s first enzyme, and fasting is a known trigger, so regular meals are protective. Patients must avoid alcohol and numerous drugs that induce attacks. The conditions are rare but dramatic, historically linked to the “vampire” legends through photosensitivity and reputed madness of sufferers, and they demand specialist management with strict trigger avoidance.