"how does it stop their itching"
I am not 100 % sure why, but I guess it has something to do with fungus,like candida or possibly mycoplasma. These things are often brought forward by Antibiotics .
In dogs vaccinations may cause extreme itching.
Boron kills mycoplasma and fungus, as they have no utilization for boron. Same with insects like mange.
This was how I got my candida (itching) under control; loads of borax and iodine, internally as well as externally.