I recently started taking ON casein and have had horrible side effects. At first I thought it was the flavor and I was just didnt like it so I bought a different flavor and loved it but the problems are still there. I take it right before bed and within 20 minutes feel like I am getting the flu... I also start to tingle in my hands and feet from low blood pressure i am guessing. When i wake up I still feel the same except i have a sore throat. I imagine that its from acid reflux and my throat gets sore. I thought i really had the flu and stopped taking it and felt 100% day later then jumped back on and instantly felt sick again.. I did some reading and read some that some people have an intolerance to casein. Does anyone else have an issue with casein? Whey protein doesnt do this to me just casein.