I have a similar condition, Aquagenic puritus, there is a Facebook group that discovered the Beta Alanine, which is usually used as a workout supplement and sold over the counter, works really well at controlling the itch. Who knows but it might help your issue as well...I’ve been taking it for 3 years with no issues...I take 750mg with any sign of itch and 1500 mg when I know it will be triggered...like before a shower.