dovobet some permanent success treating body in parts in turn

I've had ps for 20 year but lucky little itching and not visible. 5 years ago i tried dovobet everywhere for a month but it all came back. A year later i treated only a quarter of my body and only 50% came back. Same sucess on other parts of body. I now treat quarter of my body in turn once a year for a month, every 3 months and am gradually reducing ps. Also use coal tar solution on daily basis on areas not applying dovobet - this eliminates flakiness.