Garlic seems to do the trick, I give her a clove every second day like a tablet because she wont eat it. havent found anymore ticks - and we live in the sticks!!

Doxycycline is a bacteriostatic antibiotic used for the treatment of infections such as Lyme disease

What are the possible side effects of doxycycline:
If any of the following serious side effects occur, stop giving doxycycline and seek emergency veterinary medical attention; an allergic reaction (hives, difficulty breathing, swelling of the face, lips, tongue or throat); severe headache, dizziness, or blurred vision; fever; hair loss; ¿bull¿s-eye¿ lesions; vesicles around mouth, ears, and groin; urinating less than normal or not at all; dark colored urine, confusion or weakness; loss of appetite; jaundice. Continue giving doxycycline and talk to your veterinarian if any of these less serious side effects occur; mild nausea, vomiting, or diarrhea. Side effects other than those listed in this guide may also occur. Talk to your veterinarian about any side effect that is unusual or seems especially bothersome to your pet.

http://www.1800petmeds.com/Doxycycline-prod10340.html