The only time I have sucess with niacin I didn't have the flush. So, I think it's not the flush that help POIS, but the niacin itself...
Yes, I agree completely. It's sort of complicated to explain, but it seems that the flush, most times, is just "THE INDICATOR", that you have had enough niacin.
If the timing and conditions are more or less like we have established, then the flush usually indicates that you have taken the required quantity of niacin to be protected. However if for instance you have eaten soon before taking the niacin, you must take more, and the niacin delays in entering the system. Under those conditions I have been "protected" even though I ddin't get a flush. Also if you take a lot of niacin on a completely empty stomach, the flush comes fast and strong. If yo have the orgasm too quickly, you'll probably find that the niacin hasn't had time to do it's magic, and even though you had a good flush, you are not "protected".
So there are exceptions, and clearly it ISN'T the flush that protects, but the niacin.
That too goes against what the allergist thinks.