Iodine is an element that is used by the thyroid. Humans cannot produce iodine, so it must be consumed. It is added to some foods and also to salt. Iodine reduces thyroid hormone and can kill fungus, bacteria, and other microorganisms such as amoebas. Iodine deficiency is one of the most common and preventable world health problems. Most iodine is found in the ocean, where it is concentrated by sea life, particularly in seaweed. Iodine is taken by mouth to prevent and treat iodine deficiency and its consequences, including goiter and some thyroid disorders. Iodine is also used for pink eye, gum infections, wound healing, and many other conditions, but there is limited scientific evidence to support many of these uses.