Welcome! My name isXXXXX am a 2003 graduate, and currently a Medical Director of a veterinary hospital.
I am sorry to hear about this concern for Mitzi.
Well, pimples, could easily suggest a miliary dermatitis (lots of photos in yahoo.com), or a pyoderma (bacteria skin infection).
If infection is present, this would often need to be treated from the inside out. Meaning, oral antibiotics, and sometimes, even an anti-inflammatory medication as well.
It can be quite common especially for dogs with underlying allergies. So, if Mitzi's happens to lick or chew her feet a lot, which 50% of dogs with allergies like to do, than an infection stemming from allergies is another consideration.
Sometimes, endocrine conditions can cause changes of the skin as well. I would say hypothyroidism
(low thyroid hormone) and Cushing's disease, are the most popular for skin problems.
Definitely, well worth the vet visit for further evaluation and possibly some additional supportive medication.
Please let me know if there is anything I did not cover for you. I hope that information has been helpful.
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