I get drowsy from a number of things. You could also say that it is brain fog. I get very drowsy from taking antihistamine and haven't taken it in years and during the last five years I get very drowsy from taking any antioxidants like alpha lipoic acid, fulvic acid, grape seed extract, blueberry extract. I also get very drowsy from taking silica by itself or when it is added to a lot vitamins or supplements. It seems like more than half of supplements contain silica as a filler. I also get drowsy from taking colustrum, acidopholus, digestive enzymes even though when they don't contain silica. It took me a while to figure it out and of course I avoid all these supplement but I take vitamins, minerals, COQ10 as long as they don't contain silica without getting drowsy. Do you know what this could be due too?