Sweating is by far the most common skin condition fibromites have, “32%”, research has confirmed.
To outsource info on treating sweating from my symptom & treatment lists
I’m reviving this thread, as it is the most recent one of 3 which have that word or ‘perspiration’ in the title and because Ron @Fearski is still actively around… and can give us an update 
Treatments / Ideas:
Treat with tablets, mineral powders, botox, change clothes, mattresses, furosemide, HRT, Balance App by Dr. Louise Newson(?), Neat 3B face saver, oxybutenin, clonodine hydrochloride. Is it SFN or CRPS-I? Might GABA help? Or caused by meds like duloxetine & other antidepressants?).
Myself, I’ve always been a bit of a sweater, which was considerably reduced by fibro, meaning I had to change my t-shirts less often; until my TCM-acupressurist restored my cold tolerance again by activating the “inner cooking pot” which stabilized my temperature tolerance again. So I’ve never had reason to think of it in terms of fibro.
But now I’ve had a look at the studies on sweating (hyperhidrosis) on pubmed and seen
- a study that 32% of 845 fibromites suffered from hyperhidrosis, 10x more than any other single skin condition (?! Laniosz et al., 2014) Dermatologic manifestations of fibromyalgia - PubMed,
- a study that sweating may be reduced (diminished autonomic regulation) (that’d be me then) in accordance with evidence of small nerve fiber neuropathy (SFN) (Reyes Del Paso et al, 2020, (a corrrection), Correction: Reduced activity, reactivity and functionality of the sympathetic nervous system in fibromyalgia: An electrodermal study - PubMed),
- there is however a very recent study (Bailly, 2021) using sweating as a pointer to differentiate the overlap between SFN and FMS in the direction of SNF, and an old one (Collins et al, 2008) doing the same for CRPS-I - so those 2 might be diagnoses to have a look at. The challenge of differentiating fibromyalgia from small-fiber neuropathy in clinical practice - PubMed, Development of a symptoms questionnaire for complex regional pain syndrome and potentially related illnesses: the Trauma Related Neuronal Dysfunction Symptoms Inventory - PubMed,
- a study linking exaggerated muscular contraction (also muscle stiffness), sweating and constriction of blood vessels with changes in several brain neurotransmitters, particularly serotonin and norepinephrine (Marvulli et al. 2015) Objective Assessment of the Rheological Muscle Property in the Treatment of Fibromyalgia - PubMed.
The latter’d also be connected to me and also to the mention of oxybutenin and clonodine hydrochloride above, as using GABA, which drastically decreases my muscle stiffness and improves my bladder problems, I assume by changing the serotonin, whilst not making my mouth too dry, much less than meds anyway. For ‘sweaters’ it may suggest trying GABA. For me it suggests looking at my sweating more closely… - This one links sweating to duloxetine (‘Cymbalta’), so that’d also be one to watch (Ormseth et al, 2011), Duloxetine in the management of diabetic peripheral neuropathic pain - PubMed. As @Starr says above this seems also to be true of other antidepressants like Sumatriptan (‘Imitrex’).