There has been good data on the efficacy of vaccines given intradermally vs subcutaneously or intramuscularly. It actually seems to function superiorly in children and the elderly. I personally take my flu shot this way as I feel it also limits my systemic side effects.   0.1 ml of both the influenza vaccine (Fluogen) and the Herpes Zoster Vaccine (Varivax) in opposite arms seems to lessen the frequency and severity of recurrent upper respiratory tract illnesses.

I very experienced allergist and friend surprised me when he treated what I thought was just a heat rash with Permethrin.  Scabies (Sarcoptes scabiei) is an itch mite that is highly contagious.  It can be sexually transmitted for sure, but it is not always so.  It does however require close contact to spread and seems limited to humans (it is not compatible with pets).  Itching is severe and it forms papules that often blister.  Microscopy scrapings can be difficult and there is even a PCR test available.