Lugols

Lugol's solution, commonly referred to as Lugol's iodine, is a chemical solution that consists of elemental iodine (I2) and potassium iodide (KI) dissolved in water. A typical formulation contains about 5% iodine and 10% potassium iodide, which forms an iodine–iodide complex that increases solubility and stabilizes the iodine. The preparation is named after the French physician and chemist Jean Guillaume Auguste Lugol, who introduced it in 1829. Variations exist in concentration for different uses.

In medicine and biology, Lugol's solution has several applications. It has long been used as a topical antiseptic and disinfectant for skin and mucous membranes. In microbiology and histology, it serves as a reagent in starch tests (iodine yields a blue-black color with starch) and functions as the iodine component in Gram staining as a mordant to enhance dye uptake by cells. In nutrition and public health, Lugol's solution has been used as a source of dietary iodine in iodine-deficient regions and as a prophylactic measure to saturate the thyroid with iodide to reduce uptake of radioactive iodine in the event of nuclear incidents, when advised by authorities.

Safety and handling considerations are important. Lugol's solution is corrosive to skin, eyes, and mucous membranes in concentrated form and can cause irritation or chemical burns with improper use. Iodine can provoke allergic reactions in susceptible individuals and may affect thyroid function, especially in those with preexisting thyroid conditions or in pregnancy. Proper storage in a tightly closed container, protected from light, and at recommended temperatures is advised to maintain stability. Medical or prophylactic use should follow professional guidance and product labeling.

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