Although the mechanism of action of topical iodine is not fully understood, it is thought that the medication's antimicrobial effects may be due to the presence of the diatomic elemental form of iodine (free iodine). It is believed that iodine precipitates the proteins of the microorganisms by forming salts via direct halogenation. Approximately 90% of the iodine absorbed by bacterial cells reappears as the iodide, thus confirming oxidative interaction as the major bactericidal mechanism of topical iodine.
Antimicrobial activity is significantly affected by pH and is greater under acidic conditions.
Solutions of iodine usually contain potassium or sodium iodide to enhance solubility of iodine through the formation of polyiodide ion