According to Drugs.com, tincture of iodine is a medication used to both prevent and treat the bacterial skin infections that commonly develop in minor cuts, abrasions and burns. The tincture should not be used on infants or very young children, or to treat puncture wounds, deep cuts or injuries from animal bites. Most over-the-counter tincture of iodine contains the same percentage of elemental iodine as its active ingredient, along with several inactive ingredients.
The active ingredient in tincture of iodine is iodine, a naturally occurring element that is present in small amounts in drinking water, the air, soil and foods such as seaweed, milk, cheese, fish and shellfish. Iodine is essential for the production of the thyroid hormones that regulate cell metabolism and the immune system; it also has strong antibacterial properties that make it an effective preventative measure against infection. Tincture of iodine typically contains 2 percent of iodine by volume.
Tincture of iodine contains approximately 47 percent alcohol by volume. Alcohol, the general name for ethanol or ethyl alcohol, is used often used in medications as both a solvent and an antimicrobial agent. As an antimicrobial agent, alcohol helps iodine kill bacteria and prevent further microbial reproduction. In tincture of iodine, however, it mainly serves as a solvent: a liquid substance used to dissolve the other ingredients of a solution.
According to the website Cosmetics Info, deionized water is water that has been both treated and filtered to remove all toxins, ions, microbial growths and pollutants. In tincture of iodine, this treated water is used as an inert solvent for the medication's other ingredients.
Sodium iodide, a salt compound of iodine, is in tincture of iodine at 2.4 percent by volume. Sodium iodide is included in the tincture to help promote the dissolution of the pure, iodine element into the alcohol and deionized water.