I have this & could have written your post so I share your pain
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In my case, I realised that it was some (but not all) cleaning products and was diagnosed as contact dermatitis. I now wear gloves even to put washing tablets in the dishwasher, ie, no contact at all with my hands and detergents. I wear gloves when using furniture polish. Even toothpaste running down my hand sets it off, but I now have an electric toothbrush and less foaming to deal with 
Diprobase did nothing for me. In terms of potions and lotions, the only ointment that works to stop the itching is a steroid cream called Dermovate (Clobetasol). It's pretty strong apparently but I've only used it following attacks of itching and scratching, have never used it daily or anything.
Sometimes my hands have itched so much, and I've scratched them so much, my fingers swell up and then my rings are uncomfortably tight for hours after. It's miserable. Handling foods in particular tomatoes, lemons, potatoes and butter. Butter is the worst, meaning that if I bake I use disposable gloves (I would anyway for hygiene though because obviously, having hand dermatitis and baking don't go together!)
The last and most important thing I want to say to you is PLEASE wear handcream at ALL times, day and night. It helps your hand protect themselves against whatever it is that's setting it off. I have tried pretty much ALL the handcreams on the market and found most made my hands itch; the only one that doesn't and is the best, is Aveeno hand cream, it's around £5 & comes in a beige and green tube. My hands get worse in winter so I keep pairs of gloves all around - in the car, my handbag, by the door. I don't go out without gloves on past a certain temperature.
I personally think I brought this on myself through exposure to cleaning products, my mum made me clean the bathroom and kitchen from around age 11 or 12 and throughout my teens, I never used gloves (there weren't any to use) and merrily used neat bleach for years to scrub the bath. Same for washing up, never a glove in sight for years. This problem has only started in my late 20's but it's been coming on very gradually before that. I also have patches of excema on my knees and the tops of my arms are always rough and bobbly, they used to be beautiful (honestly) smooth as a baby's. I heard blackcurrant oil capsules can help so I took those for a while too but didn't keep them up.
Good luck, hope you can glean something useful out of this mound of type 