It's called Sensory Integration Disorder (SID) or Sensory Perception Disorder (SPD)
There are great books and articles/sites online about this and where to shop, things to try, etc. One book is _The Out of Sync Child_. I found it very helpful in understanding what was going on.
My daughter has this and it is a struggle for sure. Some things we do are to buy clothes at thrift stores if possible for cost-effectiveness. She'll try them on (if she is able/willing) and then if there is a problem later, we didn't spend much and I can just garage-sale or consign it and nothing really lost.
There is a great online store called SensoryEdge that has things that can help her interpret the "correct" feelings for things, pressure, etc. I highly recommend them. Once you see things she may enjoy/ may help, you can also look for those same items online at places like eBay or Amazon for better prices too. We have gotten things from the dollar store even.
Some things that help my daughter:
Tight tight bear hugs before putting on clothing if she is feeling particularly crabby or I can see that she is "off" and may be sensitive.
Having her bounce on an indoor trampoline or hang upside down off the couch, spin on a sit-and-spin or desk chair, swing, etc. if she is feeling the need for that motion.
Squeezing tactile toys like stress balls or "koosh" balls if stressed/anxious/fidgety. Sometimes doing something like this that is a fidget toy can take their minds off of the sensation of feeling "itchy," etc from clothing or whatnot.
I hope this helps. If it is really severe, you can buy special clothing online that "hug" the body to create a good pressure sensation for her, or weighted lap pads to use while she is sitting, and seam-less socks, etc.
I would also contact an Occupational Therapist if it is really interfering with her ability to function. They can give you great ideas and work with her to help her process things better as well as coping strategies for the both of you!
M.
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