Rockweed, also known as bladderwrack, is a member of the Fucaceae family. It can be found on the Atlantic and Pacific coasts, the North Sea coast, and the western Baltic coast. The thallus of the plant can be used for medicinal purposes. Rockweed contains iodine, which is important to the thyroid hormone, as well as polysaccharides and polyphenols. Rockweed has been used for thyroid disorders, digestive disorders, anxiety, bronchitis, rheumatism, constipation, and other ailments. Bladderwrack is not to be confused with bladderwort.