Even certain cotton processing (occasionally even organic) gives me problems, even ‘detectable’ by my wife… 
Unfortunately even “100% cotton” is not 100% cotton…
As far as I’ve read however, many fibromites have like non-fibromites no problems with synthetics etc. despite oversensitivity to other things, esp. heat/cold, certain meds, then light & sound etc. Question is also if it causes pain (in this case tactile/static and/or mechanical/dynamic, praps even thermal allodynia), overheating, the smell irritates etc. (In my case it’s sort of overheating, pre-fibro).
Researching suitable clothing textiles for fibromites I found:
fibromyalgiaresources: soft materials, incl. fleece (so synthetic), but also things loose & light like silk.
fightfibromyalgia: clothing as trigger is a fairly new concept: belts, waistbands, tight elastic socks, detergents. Next to the fairly natural cotton, silk and satin: stretchy knits, fleece and flannel, usually all synthetic. fibrowomen: similar, shorter.
verywellthealth: Focus on allodynia. Similar, adding viscose/rayon (part-synthetic). Wear less at home… contradicts weighted blankets.
healthcentral (Karen Lee Richards): soft cotton and polyester knits, watch for fabric & seams, style & size: neck & waist areas, underwear. fibromyalgia-symptoms: similar, shorter.
You can get weighted blankets with only organic cotton and glass beads from cura of Sweden (price crash) and now sweet zzz mattress (maybe they made cura ‘come down’). However I’ve hardly seen this discussed much, it’d just be my solution if my tests had worked out.
fedupwithfatigue/nationalpainreport (Donna Gregory) claims the weighted blankets stimulate the skin to release serotonin, which calms, “like a hug from someone we love does”. (Now there’s a challenge: Hugs are brilliant, but not longer than a few minutes… )
Others say it reduces anxiety, depression, ADHD, PTSD, autism, feel safer, protected.
There are over 200 studies on them on pubmed, esp. focusing on anxiety, however 0 on fibromyalgia (also 0 on blankets or cotton).
The 2 most recent ones are of mixed opinion whether there is enough evidence or not:
Study by Ekholm et al, 2020: “Weighted chain blankets are an effective and safe intervention for insomnia in patients with major depressive disorder, bipolar disorder, generalized anxiety disorder, or attention deficit hyperactivity disorder, also improving daytime symptoms and levels of activity.”
Review by Eron et al, 2020: “Weighted blankets may be an appropriate therapeutic tool in reducing anxiety; however, there is not enough evidence to suggest they are helpful with insomnia.”
I think adding blankets hasn’t helped me, so weights won’t either, partly cos they make it harder to change/twist my positions. But I’m also thinking from recent experience that the pressure of my body on the mattress gets too high (altho I’ve softened those areas with toppers).
If I were anxious or depressive, hadn’t got control of my hyperactivity and traumata, had less problems with long hugs, then I’d think it likely I’d try it more… But my wife remembers someone with anxiety etc. using a nursing/breastfeeding pillow and also myself, sometimes having used a hugging pillow, as alternatives.
A selection of best forum-posts here on touch sensitivity / allodynia: Allodynia & Tactile Allodynia, a bit about bed clothes on this mattress-thread (series of light cotton quilts, cuddling pillows; Cuddle Ewe pillows for fibromyalgia): What is the best mattress for Fibro? - #2 by GoLightly and clothing: Anyone have problems with clothing? - #5 by riverofsurvival (neuropathy, allergies, roll pillows for less bed sheets contact, stretch pants, fabric conditioner for softening, neurodermatitis: nothing scratchy or too soft, stretchy but not ‘plastic’(?), tags, dry skin, sweating, hard to go out, Princess & Pea, Ehlers Danlos Syndrome(s) = EDS (13 types), denim/jeans, meds & anxiety as triggers) & Has anyone found clothing that doesn't hurt? & My clothes are already making me nuts! - #6 by Auburnm, Sensitive skin hurts: Have you ever had this happen to you?
