The steroid probably made it much more likely it would come back, and antibiotics may very well do the same thing, as both
types of drugs can adversely affect the immune system overall. But without a diagnosis, you can't really make a decision on how to treat it, and if it's not an allergy, it could be a fungus, it could be bacterial, it could be some type of bug sting or bug bite -- almost sounds like he sat in an ant hill -- so you just have to find a better doctor, I think.