Have you looked into Aquagenic Pruritus? Itch from water contact…within a few minutes of getting out of the shower, my arms and legs itch severely. If this sounds familiar to you, you may want to look at the Aquagenic Puritas a support Facebook group.
Several years ago, someone there discovered that when they Took their pre-workout supplement, they didn’t itch. They isolated it to beta alanine, which is an over the counter amino acid supplement. I take 1500 mg 20 minutes before showering and I have a little to no itch.