Kelp is an herbal medicine taken from brown algae in salt water. It is used to treat weight loss, high blood pressure, low thyroid hormone, and arthritis.Kelp is also used to make the cervix (mouth of womb) open for childbirth or to end an early pregnancy. It is usually used as a source of iodine or salt.Other names for Kelp include: Laminaria digitata, Laminaria japonica, Laminaria saccharina, Macrocystis pyrifera, Brown Algae, Horsetail, Sea Girdles, Seaweed, Sugar Wrack, Brown Seaweed, Algae, and Tangleweed.t is usually used as a source of iodine or salt. Other names for Kelp include: Laminaria digitata, Laminaria japonica, Laminaria saccharina, Macrocystis pyrifera, Brown Algae, Horsetail, Sea Girdles, Seaweed, Sugar Wrack, Brown Seaweed, Algae, and Tangleweed.