So this reply is going to be TMI for those who don't suffer. Look away if you must, LOL!
I have had simpy horrible butt-pain recently. I went on Amazon, looked up Preparation H and started reading comments from other users. Many recommended this stuff, so I bought it:
It's probably the best thing I've found for soothing/cooling my poor butt. It has a kind-of minty effect somehow. That plus some witch hazel, which I gently apply beforehand, with a baby wipe. (Preparation H sells wipes that already have witch hazel, and I bought those too, but they don't have enough, IMO.) People on Amazon recommended some kind of pill to go with the ointment, and I bought that but it made my GERD flare up (I do take an Rx PPI twice a day), so I quit taking them. The ointment plus an analgesic like Tylenol helped me get to sleep.
I also tried the Lidocaine - I agree, it wears off after about 5 minutes. Other people have recommended Desitin, but haven't tried that yet, and of course good ole Prep H.
This is a seriously life-affecting issue, believe me I know. I hope your C.S. can help you, and I hope these recommendations help in the meantime.
What finally helped was cutting back on the Miralax. You know, this hi-protein diet that VSG-ers are supposed to be on, even with high fat, you have to do SOMETHING to get things moving. But I was taking Miralax every day, and my "movements" were so loose they were making my hemmorhoids so much worse! I now take the Miralax every other day, which is MUCH better, it produces a more normal bowel movement. So I now have to use the witch hazel / ointment occasionally.
Something else occurred to me, that a probiotic might help you. If it's some kind of bacteria that's creating the dermatitis, perhaps a more beneficial bacterial mix would help?