You have not specified what tablets were given to your dog. Firstly he has to find out the caue for the infection. This could be some food allergy or even some contact allergy too. If it is seasonal, which is quite common in these months, you probably would know. Dogs generally develop folliculitis and for that they need to be put on an appropriate antibiotic course including taking care that the source of infection has ben identified and removed. Ivrmectin is a long course, you can ontinue with that but also try out with sporidex 500mg twice a day for atleast 3-4 weeks. Give once a week oil massage at night (added with camphor) which is to be followed by a bath in the morning. Also try posting some pics of the dog so that it is easy to come to a diagnosis.