I've had this too. It drove me mad! At first I thought they were insect bites as I'd been walking in an area with lots of midges/ gnats but the condition kept returning. I'm still not sure what is causing it but it's under control at the moment.I found Nizoral shampoo helped. Head and Shoulders Itchy Scalp shampoo also deadened the itchiness temporarily. Hope this helps.
I was diagnosed with diabetes in 2013. I didn't react to it, since I had had a number of symptoms which identified me as having the the signs long before I was diagnosed.. I was also working with a colleague who had type 1 who had told me the itching was one of the signs of diabetes. Since being diagnosed my weight has gone up as well as down.
There is something I have noticed about my own diabetes it that when I walk for any length of time I start to get an itchy scalp. This is has become a bit of a nuisance I had thought was it due to me walking. I now have realized that when I walk and I get my itchy scalp my sugar has lowered. When I arrive back after my walk I take something sweet. Within a couple of minutes of taking something sweet, including honey, my itching has stopped and my head and the rest of me feels fine. No itching, No blurred vision. I am not testing since the NHS do not now issue the test strips to type 2 diabetics. It has come about that if your diabetic today and not meaning to make this political, if you are not being issued with test strips, it is very much down to yourself, to know your own body and the signs it give you. I too have tried the shampoo's, but only to have the itching come back. I am not saying it is the same for yourself, but if like me you walk or do anything physical and then find you are itching or have some other reaction, then you can always try something sweet and see whether it has any effect. If it does work, then you may need to see your diabetic nurse and let him / her know. Keep an eye on those carbs.