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As I'm 72 years old, diagnosed in 1985, but now believe had type 2 diabetes from childhood, I'm ahead of you! Things I've tried include codeine phosphate, (fairly effective but nasty stuff), Dettol antiseptic in bathwater then having a long bath, (effective but see below), and sunbathing! I tried other things without success.
I found that the codeine works, but only for an hour or two, leaving the symptoms slowly driving me mad until the next dose was due. OK but only for "emergencies".
Putting Dettol in my bath usually resulted in increased itching, but after the 2nd bath with Dettol some days later, the itching had gone. This was my first real "clue".
Then I realised that the problem seemed to go away late summer for a few months. A doctor suggested that this might relate to vitamin D gained from sunbathing. That was a plausible theory, aided by having longer summer holidays in recent years with the benefit lasting longer into the winter.
This year has been different. Last summer I had the longest summer holiday of my life, (four weeks). I spent a lot of time in the sun, and now it's late February still am almost completely itch free.
CONCLUSION
The Codeine answer is only pain and itching relief, it isn't a cure.
Why did Dettol work? Effective but it seemed odd.
Sunbathing. Why did that work? It can't be vitamin d, I'm sure there's no vitamin d benefit left now it's around 6 months since my last time in the sun.
Then a brainwave flash, I think I have it. I think that high blood sugars, maybe years ago led to high sugar on the surface of my skin feeding a viral, bacterial or fungal infection to my skin. The Dettol attacks it, hence extra itching at first, then a benefit for a while with the infection eventually creeping back.
Ultra violet light, (essential for sunbathing!), kills viral and bacterial infections and may also kill fungal infections. I think that, last summer, four weeks of holiday, often in the sun, has "disinfected me" from something that has been with me for a great many years. It'll return, but there's next summer's holiday on a beach to help again!
I hope that this gives you some ideas. For Dettol use about a capfull, (the cap of the Dettol bottle), in a normal bath.
Sunbathing - not enough for sunburn, obviously.
No sun? Try an ultra violet sun tanning sunlamp. If using a sunlamp, wear a swimming costume or underwear to protect the body's "vital parts". I sunbathe in swimming trunks, the small covered area doesn't seem to be a problem. Probably with most of the skin protected, the small covered area means not enough infection is left to cause serious problems.
Good luck!
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