You say that is not the "only form of abuse" you've seen with the kitten, then HELP IT. Call someone - humane society, the SPCA - report what you've told us here
and in the meantime, call a vet and ask the question about the benadryl, and if you need to, take the kitten to get some help.
Modified CG since Dec 2011
Growing out super short cut
High porosity, fine, unknown curl type, somewhere in the 2s at the moment
Mostly low poo
Current rotation includes:
Wash: Yes To Carrots -Condition: Yes to Cucumber, Nature's Gate Jojoba, One C - Stylers: Deva volumizing foam, Deva UDG B'Leave In, Foxy Curls Hi-Def Curl spray