My daughter suffers from RSD (among other things), and we recently discovered that Benadryl helps her pain immensely. No other meds have ever provided relief; and although we too do not know why it helps, we are very thankful that it does. She cannot take oral meds as she has gastroparesis so she receives IV Beneadryl thru her port, with the pain relief being almost immediate.

I correspond with another RSD Mom on this forum, and she recently shared that there is a doctor who uses Benadryl infusions to diagnose abdominal RSD -- if the pain responds, he knows that it is in fact RSD.

For these reasons, I found your post to be very interesting and hope that others can provide additional insight.