Hello,my son i years of age. Three weeks ago ablister appeared on his knee, he picked it it became infected. He was put on antibiotic course which he competed with fucifdin oitment. all seemed wellas it went away. 2 days ago however at about 2 inces from the previous site anoteher appeared and to today another, he is again on antibiotce however i have a feeling there is more going on,...could this be a parasitic infection photos available if this will help