Povidone iodine is iodine bound to a water soluble polymer called polyvinylpyrrolidone. Think of the polymer as a reservoir. It gives up only a little free iodine at a time. That little is enough to kill bacteria, fungi and viruses, and too little to burn tissue. Slow release is the whole trick, and it is why cleaning a grazed knee with povidone iodine does not make anyone gasp the way iodine tincture does. Where iodine came from: seaweed ash, gunpowder and a purple vapor There is a brown bottle in most household medicine cabinets. A child scrapes a knee, somebody dabs it with a cotton swab, nobody screams, and the…