Keloid isn't a chemical, it's a sort of scar tissue that forms when there's not the right sort of nutrients available to the body to form the right healing, and hormones are wonky. Keloid scar tissue is an ideal place to paint iodine.
Chloride is good, Chlorine's probably the nasty one you're thinking of. ;)
I would think that Iodine is best taken orally or on intact skin where blood flow will carry the Iodine to the wounds that needs healing. Right into wounds... Well, Iodine encourages the breakdown of unhealthy tissues. I used 20%, Lugols on my foot after a big bruise on my inner thigh from wiping out on my moped.
2 weeks later and the bruise was really well healing.
A paleo diet and all the iodine co-factors are the other clues to the healing puzzle in my case- quality meats and organic veg supply good amino acids for building the body.
Keloid scar could be addressed with applying hydrogen peroxoid and iodine several times a day... But can be a little painful(!) H2O2 (Hydrogen-Peroxid) and iodine work together to tell the immune system to break down and rebuild the tissue at -that- specific site