Hve been unable to track down cause of recurring abnormal reaction. My body goes on fire and I become red and blotchy all over, feels like a bad sunburn and itches unbearably. After benadryl dose, symptoms subside in about 4-5 hours. Been trying to figure out cause. Am 74 yrs old, very slim, 5' tall and have been taking D3 1000 iu plus multi-vitamin with 800 IUs of D. Could this be a case of Vit D toxiccity? Have lost appetite, weight and feel tired which is unusual for me.