I had a long-lasting problem from oral penicillin.
Then again, for a very long time, from plants of the nightshade family...tomatoes, white potatoes, sweet peppers, eggplant, and tobacco.
I'd get tiny, pin-head blisters on my hands and feet, and the outside of my thighs, that would set 3 or 4 inch areas of my skin to itching as though I had been inoculated with poison.
I wanted to tear the skin for relief.
Some lotions or spreads helped somewhat, for a time, but the best was icy water.
I was eating many organic cherry tomatoes at the first of this second round of itchiness, and, when my feet were itching terribly, my husband brought me a five-gallon pail of cold water with ice in it. I was grateful for the relief.
A few months later I was on a flying trip, and, right after the airplane breakfast of scrambled eggs my hands began to itch something awful.
The stewardess was alarmed at how huge and red they became and brought me a bag of ice. I plunged my hands in, and didn't take them out until the ice had completely melted.
I wouldn't recommend putting ones hands, or any skin, directly on to ice, but at that time it 'hurt so good', if you know what I mean.
That trip continued with a number of other miseries, until we left, early. Home was a great relief, and I had learned about plants of the nightshade family, quit them, except smoking, and suffered no more.
What I have been doing in the years since, including rounds of Humaworm, has cleared me of enough toxic substances/parasites that I no longer have to avoid foods, I believe.
We have potatoes, tomatoes, etc., without incident...although I must admit that I don't have many at a time...with a fairly long rest in between.
My heart goes out to all who suffer. I wouldn't have it again for all the tea in China.
I've also had that burning/stinging rash under the breasts and in other folds of the body. R.G.'s cream helps wonderfully.
I haven't tried the 1% solution bath of crystal mineral salts specifically for itching, but I wouldn't be surprised that would be grand.
Hope this helps.