Bulldogs World

I had posted a while back that our bulldog puppy had developed this little area on the top of her head that was at first a small bump then lost all the hair. I took her to the vet to rule out demodex and he gave me a topical antibiotic in case it was a staph infection. It was all but cleared up and she got her heart worm pill for this month and now bump is back and hair is gone. When I think back this all started after a dose of heart worm preventative. Has anyone else ever experienced anything like this? What do you guys use for your bulldogs?