My friend's husband gets really bad cystic acne, apparently everywhere, but especially on his back. I was unaware of this until she was telling me of draining and cleaning a lesion under his arm... this lesion consisted of several smaller lesions all draining into a large cyst.
I wondered why he left his shirt on when we went swimming, now I know!
This condition has never been formally diagnosed as cystic acne. They have no health insurance and the only other topical treatment they've tried is neosporin. Liz tells me that the healing of the drained cysts can take months, for one of this size, close to a year!
So, I suggested they try some iodine salve. The results are pretty amazing. Within a few days the lesion has healed. Hubby says it's a miracle:)
There's information on topical iodine and wound care all over the web. Here's a good reference: