Hi,
Ive been suffering this hell for 17 years.....i got to a point a couple of months ago, where i couldnt handle it anymore...on top of my sweating every where all day every day, i get hyperthermia......, my body temperature drops so low, i start shaking out of control......., a couple of weeks ago i had what was a suspected heart attack/panic attack......., it turned out i was having a serious attack of hyperthermia, that started out with a cold all over sweat 'HH', i then callapsed, couldnt breath, i thought i was going to die!
Like your good self, i have had all the usual tests, bloodworks etc etc etc......
No underlying cause......, i knew there was'nt......, i had an accident in 1993, resullting in a back and neck injury, 2 years later i started to sweat, and over the years its got so bad, it had got to the point where i couldnt live like this any more.
Any way......., im not sure if you have already been recommended this , my GP has prescribed me a drug called 'OXYBUTYNIN' its for urinary problems, but has been proved to work for people suffering 'hyperhidrosis'..., its a small tablet, that is to be taken 3 x a day, 4 in my case!...
This might help you, with you having no underlying cause.
Within 1 hour of taking oxybutynin/ditropan, IT WORKED..........., and it worked very well !!
However , it does have side effects : this comes in the form of a dry mouth, " some people cant handle the dry mouth ", but compared to sweating all the time, it is the smallest of prices to pay .
Im about to ask my GP, if i can see a specialist concerning this, I need a MRI scan, to see if i did suffer an internal injury be it head or spine..
I may have a rare sydrome called 'episodic hyperhidrosis with hyperthermia'...., all my symptoms point to this......,
Ive since done some research, my hyperhidrosis, could come from a few reasons, head injury,spinal injury and also COLD INJURY i was sublected to extreme cold temperature's when in scotland around the time the 'HH' started, ( i lived somewhere with very bad heating to no heating while it was minus 28 out side !
( this is no exageration, when it was -28, my house was that cold, it was warmer to go out for a walk out side than it was to stay in, this could be a big factor in the cause, for me...)
I also like your self have not met any one with this, and ive come to understand, most people with hyperhidrosis, Hide it, and hide it very well, i know this because, not one of my friends ever knew, a couple picked up on my very wet hands, but never commented, and also i have kind of hid myself away for a very long time....., I think im safe to say, this is Life ruining.... ive only just now started to tell my friends, its so distressing..and is a huge factor in depression..., but you are not alone anymore, talk to people, let them know.......
Anyway, i do hope ive been of help, and i hope you get the help you need, if your GP won't prescribe this, try another GP till they do.....,
Keep well........, don't let this beat you

Take the very best of care.
martin.
PS, ive a blog under : ditropan/oxybutynin on this forum, that i added last night..