hot water kills them instantly...
whereas... whatever chemicals we might apply will take time... even permethrin takes up to 24 hours... and is really not 100% effective...
i think the thing about scabies is that it is a new bug for most of us... one that i was totally unaware existed until i got them on me... and what i found was that it was an absolute torment... especially the fact that they seem to pick the middle of the night while you're sleeping to do their worse... to be awakened at 2:am in the morning with the most horrible itching one could ever experience is something that everyone should experience... at least once...
in the beginning... i tried everything... and nothing i tried would get rid of them... nothing i tried worked... so eventually i had to go to the doctor... who diagnosed it as scabies and gave me the prescription for permethrin... which is not cheap either... and also... the fact that everytime you happen to have a new outbreak you're going to have to go back to the doctor to get another prescription...
but if you think about it... these bugs live just below the surface of the skin... and rely on the reliably constant temp of the host body... well... one of my many hobies in years past was tropical fish... and fish will die if they are exposed to a sudden temp change... just a difference of merely 2 degrees in temp is enough to kill them... anyhow... this gave me the idea of trying the hot water... since then... i've changed the way i shower... i always use very hot water... as hot as i can stand it... but imagine if one were to go to the opposite extremes with cold water that it would work equally as well... one would think it would depend mostly on that sudden change in temperature that would be most effective to kill them...
but haven't been brave enough to try the cold water treatment yet... seems i'm more prone to being in hot water... story of my life... lol... ;-)
truthfully... (knock on wood)... i have not been bothered with those horrible little pests in quite some time now... but if and when they ever return i know what to do to get rid of them...
take care...
and best of luck to you...