A blog called BotoxCorner discusses the use of Botox to treat hyperhidrosis. It was hard to tell who is writing this blog and why, and whether he has any conflicts of interest that would make his blog less trustworthy. But it is worth at least checking out.
I saw Botox treatments (underarms and palms) administered at a medical conference. The doctor used ice cubes to numb the area just before the shots. The patients flinched a little but did not seem to be in major pain. There was slight bleeding from the area covered. Palmar injections are said to be more painful than axilliary injections. Iontophoresis seems to be a preferable option for most people.
The other problem with Botox is that it is expensive and not always covered by insurance.
I am wavering between treating my palmar hyperhidrosis and not treating it. I seem to be doing OK without the treatment.