Here I am almost 9 years in and going through another round of startup. Like others I have suddenly come down with the first colds and such I have had in decades. I had let my proportion of 5 star mb12 slip too low for my CNS penetrating doses. I decided to try the 50mg test and boy did it hit me all over again, a new round of CNS startup. At the same time I have managed to keep out of paradoxical folate deficiency enough that I haven't had IBS for almost 2 months now, just a few hints of cheilitis which allowed me to take corrective action quickly enough. Just as I had a series of colds and miscellaneous viruses in the first 6 months after starting I am having number 2 such episode in the past 2 months. My question, as others have been asking is What has been changing that now I am having these colds and things? I know that the folate brings down hypersensitivity to all sorts of things. Are these current illnesses then a result of returning to normal immune system from one that was hyper? Or is it now reacting to viruses that it wasn't able to take on previously. Others have mentioned about such colds and such. I am having the first stuffy sinuses in decades. Is this from another induced deficiency now that finally for the first time in my life I have enough folate to stay out of deficiency? Or is this indeed a better normal working immune system. For decades there has been wonder about a little acknowledged phenominon, that heroin addicts had relatively few colds and flu. That was attributed to some protective effect of the opioid. I'm wondering it maybe it wasn't caused by a poor diet lacking folate and/or b12 and making the immune system hypersensitive. I have lots of questions and no answers about how this could be casued.