The fibres are probably from clothing that sticks to the slightly-weeping wounds.
I have this problem myself with a small wound on my foot. I have to use tweezers to remove the fibres that have come off my sock.
This is a great common-sensical surmise. For people who have had the tick-borne disease, the little fibers are karetin-based and are grown under and inside of the skin, leading to pain and itching. The people who do not have these probably have some sort of psychological problem.
If I recall correctly, very young children (under 2 years of age) children have had these fibers. How terrible for a young child who can't understand what is happening. This is part of the evidence for me that this is not just a psychological illness, but a physical one with documented and testable causes. The people whose blood tests show they have not had the tick-borne disease also do not have the karetin fibers in the skin.
I think of this situation in terms of a Venn diagram of overlapping circles. The bigger circle contains the psychological sufferers; the smaller circle contains the tick-born illness sufferers. Since in the US, most people who experience itching and sensations of movement under their skin have psych problems, the medical response is that ALL of these symptoms are psychological. Compounding the medical misdiagnosis is that the tick-based illness seems to be new for the US, and so there is no good source for information about this. Physicians, like most people, go for the easiest, most likely cause. A new, rare disease with symptoms coinciding with symptoms of an established disease is unlikely to get the attention it deserves.
My personal experience causes me to empathize with the real sufferers (! Alert to both TMI and Rant below!):
I have endured great pain frequently over most of my adult life with a medical condition which doctors refused to recognize because their tests indicated everything was OK. (But other types of tests which are not recognized by medical
insurance indicated a clear problem.) Also, it falls between two different medical specialties, so it was nobody's baby. 100% of all my doctors until I was in my 50s gently told me that I needed psychological counseling. This condition caused pain and other effects such that I was sometimes in the hospital for days. In 2010, it landed me in the critical care unit after emergency surgery for multiple stomach ulcers that had ruptured and caused peritonitis. Four years ago, the US AMA recognized this was a real disease, and so getting the medicine I needed became much easier. Until then, I had to search for independent physicians who would prescribe off-label for me. I told them what to prescribe based on my symptoms and my hypothesis of what was going on. The drug and the dose are what I came up with myself after I got out of the hospital in 2010 and decided I needed to take matters into my own hands. What I dealt with on my own for all those decades is now considered a "life-threatening" situation requiring immediate, emergency medical attention. No shit, Sherlock.
My experience is very like the Morgellens sufferers' experience. A real, rare, "new" disease; some symptoms in common with people who have psychological problems.