Bookie's lesions could be caused by bacterial, parasitic or fungal infection, dietary or environmental allergies or sensitivities, immune system disorders, or a combination of the above. I recommend making an appointment to have Bookie seen by your veterinarian to help determine the cause of the lesions you’ve noticed and to make sure they are treated appropriately. The vet will likely want to look at a sample from the area under the microscope to determine if there is an infection and to figure out what medication is appropriate for treatment. It is not appropriate to start treating with antibiotics without further diagnostics, as it leads to antibiotic resistance, and may not be effective.