From my experience with scabies before and after treatment cutting of the nails and cleaning is utmost imporatant. I was reinfected with scabies about 3 times because these things were getting under my nails or around the edges of my fingers and toes. I would concentrate treatment if you keep gettiing reinfected to places like folds of skin or thicker areas of the body like hands, feet, knee caps and elbows. Likely your skin is so thick the treatment is not penetrating your skin, there is a good skin exfoliator on this forum that gives a free trial, this stuff is miracle stuff as it takes all the layers off your skin within days which sheds the mites and the debris and stop itching immediately. See with scabies and post scabies your skin will continue to itch like you have active scabies until you properly exfoliate your skin.
Hope this helps