Uncontrollable itching - driving me crazy!

I am new to this forum, so I'm unsure of where exactly to post this. However, I have diabetes and I keep wondering if the itching I am plagued with is blood sugar related. I was diagnosed 3 years ago. I'm on metformin, onglyza and diamicron. My blood sugar was good until this past summer. I am on two blood pressure meds that caution being out in the sun too long. I started getting a rash on my face and neck every time I was out even with protection. It wasn't very itchy, just ugly. However, the cortisone cream I was using wasn't doing the job and the rash slowly crept down my chest and on my right forearm. I felt lousy and my blood sugar was a little higher than it usually is. Finally, the rash was so terribly inflamed, the Dr put me on a short course of prednisone. It helped as long as I was on it, but as soon as I was done it, it came back and spread all over, being very itchy. It looked like the eczema I had had before, so got an appointment with a dermotologist. She started me on plaquenil and stepped up the cortisone cream usage. The rash is mostly gone, but in the last week or so, I've developed intense itching. I've been on atarax - an anihistimine - for awhile, but it doesn't seem to be helping anymore. The itching is worse at night. Seems to get really bad as soon as I'm in bed and trying to sleep. It doesn't wake me up, so I try really hard to get to sleep. Unfortunately, like tonight it was suddenly unbearable. My scalp, back, backs of thighs, tops of feet and ankles itched so badly I had to get up. The dermo. said night itching is common, as our cortisol levels fall at night to help us sleep and mine could be lower than normal. To me, it seems sort of nerve related. I notice it whenever I've had a temperature change. ie: back sweating from sitting, going from a warm living room to a cold bedroom, etc. I would welcome any thoughts or suggestions. Thanks

I have done all the testing for allergies, environment and meds. The dermo's only suggestion was the cortisol thing. No one has mentioned doing a hormone test to determine my cortisol levels. I am just at my wit's end!

Well, I've gone off most my meds and saw no change nor any change when reintroducing them. Anyone else had itching problems?

Thanks, do you know if the lidocaine cream is available OTC in Canada. I don't know where you are from, so thought I'd ask. It's worth a try as all the eczema lotions (Aveeno) don't last very long.