What Causes Pus Filled Boils On Waist Inspite Of Using Triple Antibiotic Cream?

My 13 year old son has recently experienced 2 boil like sores on his waist line. The first one appeared, and we almost thought it was an infected insect or spider bite. We watched it closely and treated it by using peroxide and triple antibiotic ointment. The sore became rather large and drained pus and blood, yet continued to improve daily until it went away. It did leave a patch of dry, flaky skin and a scar with discoloration (purplish-red color). About a week or 2 after the boil healed, another one popped up in the same area about 2 inches from where the first one appeared. The same exact symptoms... soreness and redness, swelling until pus and blood drained from it, leaving flaky skin and a small scar. Could you tell me what the possible causes of this would be and how to treat it if it happens again? Should I have him see his pediatrician? Thank you.