Benadryl is not a prescription in the US (it’s an OTC allergy med). One dose of IV (or pill form) of Benadryl prior to IVIG would not lead to a two month remission. My pre-meds for IVIG were Atarax (b/c I do better w/it than Benadryl), Pepcid & Tylenol. For me (not speaking for
@crypt0cu1t) the improvement in overall symptoms, and the remission from MCAS, was due to the IVIG.
I had been hospitalized one year prior to starting IVIG and was getting IV Benadryl 2x/day in the hosptial (and then Benadryl injections once I went home) but it did not bring about remission and I ended up developing a toxicity to it. The IVIG infusion pre-meds are short-lived in their reactions (unless someone had a high dose of something like Decadron) but even that would not bring a two month remission from a single dose.