Hi Dear, Welcome to HCM. Understanding your concern. As per your query your child have symptoms of swollen skin tags oozing white puss on buttocks, well skin tags are very common and generally occur after midlife. These are mainly due to result of skin rubbing against skin that is why generally found in skin creases and folds..They are said to be caused by bunches of collagen and blood vessels which are trapped inside thicker bits of skin. They are usually harmless. Need not to worry. You should maintain complete hygiene and apply topical antibacterial ointment such as bacitracin on them. I would suggest you to consult plastic surgeon for proper evaluation of the condition . Doctor may remove it surgically under local anesthesia or do cryosurgery or use laser therapy . Hope your concern has been resolved. Get Well Soon. Best Wishes, Dr. Harry Maheshwari