Betadine is the worst for skin prep. But we use it all the time. If you read the bottle it tells you that betadine will break down roughly at about body temperature (36.4 degrees)
When i was in nursing school i took 5 different kinds of scrub soaps to microbiology class. I put each one on a petri dish and swabbed lots of bacteria. Chlorahexidine(hibacleanse) did the best and betadine did the absolute worst. The petri dish overflowed with colonies. YUK

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And even worst, many moons (years) ago we used to put betadine in the warmer for comfort measures. I guess that was like painting on water. who knows.......... anyway i like to use duraprep(has alcohol) or chlorohexidine. But those are not the prep of choice usually.