I got very ill from a strange cat scratch. Finally, after being so diagnosed, I started taking 500 mg. of tetracycline twice a day. It took 5 days before I was healed and back to my normal self. Since your son was taking a form of penicillin, he would have to refrain from ingesting any dairy products as they tend to have a negative effect on the healing process. Since your son is only 11, his dosage may need to be half of what I took; however, your doctor will have to make this call.