I know ivomec is used to treat worms along with sucking & biting lice & mange mites. Doc drew blood from Baxter before he would give him the shots & checked for heartworms & lymes disease. The itching has stopped don't know if it is the steroids or the ivomec? Doc said the steroids would last up to six weeks. Yeast infection can be internal too. So wondered about it too? Maybe I should be giving Baxter yougart if we are talking about the same yeast infection that humans get? I know birds can get a yeast infection in their crops & yogurt can be used to get rid of the infection. Some questions to ask the veterinary for sure.