I didn't read all the replies but has she been checked for 'under the skin' MITES ?
A friend thought her yorkie had bad allergies - she TORE up her little foot so bad it looked like Raw Hamburger - she finally had them do a skin scraping and it turned out she had MITES
Now that she's getting the right antibiotics - she is healing great - but her baby almost lost her foot to those nasty creatures.....this happened in Houston...so it could be something to ask about - if they're here - chances are they're all over the country....
Her other Yorkie did NOT get them either - go figure .....
I hope your baby feels better...that has to be so hard to deal with ....we hate seeing them suffer....