Itching has many causes and cannot be pinned to a single vitamin. Still, certain high-dose supplements can contribute. High-dose **niacin (B3)** may cause flushing with redness and itching sensations. Excess fat-soluble vitamins (A, D, E, K) carry greater toxicity potential; **vitamin A** toxicity can involve dry, itchy skin. Very high vitamin D may cause hypercalcemia with various symptoms. For vitamin K, toxicity is less common, but drug interaction (warfarin) is the major safety issue. Persistent itching warrants evaluation for allergy, liver/bile issues, kidney function, skin conditions, and medications.