Hi Kaethy, Sounds like Ginger found the Frontline irritating and scratched and in doing so set herself a nice "hotspot".
Here's my recommendation:-) Trim the fur from the affected areas with a one inch margin and bathe gently with Hibitaine Soap, rinse and pat dry with paper towel. Do not rub or use a heated dryer but you can use the dryer with a cool setting but shouldn't be necessary. Ask the vet for a corticosteroid topical spray, I use Topagen, and spritz twice a day. DO NOT use polysporin as it has a greasy base and hot spots need air to heal. If the area spreads and looks particularly nasty or she raises a temperature (normal is 38.5C) then she needs antibiotics. You can also give Benedryl or other antihistimine and your vet can prescribe dosage. Keep her from scratching further and if necessary put an old cotton T-Shirt on her. Rose T.
