Of the elements less often recognised as metalloids, beryllium and lead are noted for their toxicity; lead arsenate has been extensively used as an insecticide. Sulfur is one of the oldest of the fungicides and pesticides. Phosphorus, sulfur, zinc, selenium, and iodine are essential nutrients, and aluminium, tin, and lead may be. Sulfur, gallium, selenium, iodine, and bismuth have medicinal applications. Sulfur is a constituent of sulfonamide drugs, still widely used for conditions such as acne and urinary tract infections. Gallium nitrate is used to treat the side effects of cancer; gallium citrate, a radiopharmaceutical, facilitates imaging of inflamed body areas. Selenium sulfide is used in medicinal shampoos and to treat skin infections such as tinea versicolor. Iodine is used as a disinfectant in various forms. Bismuth is an ingredient in some antibacterials.