I won't pretend to know what this is, but I can tell you what I have seen.
I have isolated a thread-like parasite which causes extreme itch and flakiness in the scalp. It may be a form of fungus, but grows like a worm.
I know that parasitologists have run across this, but nobody is making speculations about it.
I personally think it is a type of parasitic "cross" between a plant and nematode.

There is also the possibility of demodex mites.
If you have a certain blood-type, they could go nuts on you. These skin mites are a normal inhabitant of the human body. They also cause acne.

The mites can be controlled. The other thing may be a co-factor in a wider problem, which includes other parasites.

This is all just talk, and not meant to be advice or anything.

Some people have had very good success with extreme salt baths. It takes some time, but can be very effective in cases like this---IMO---------------Shroom

If nothing else has worked, get a bottle of gentian violet and paint yourself purple. The itching will go away and you will feel instant relief, but you will be purple. Most of my stuff went away in less than ten days, I did not go anywhere. I still have lingering skin issues that I'm able to deal with in a less aggresive manner, if I have something that I can cover I paint it purple and it goes away. Have you tried any H202? Iodine?

Coconut oil does marvel for the skin, it is an antifungal and will kill the bug shroom talked about. Most skin infections are due to fungus so an antifungal shall do the trick.

Zinc (in cream on your skin but also as a supplement) helps against itchy skin in general.

Jhan