Four seaweeds are commonly used in Chinese medicine:

• The kelps Saccharina japonica and Ecklonia kurome as sources of kunbu (Saccharina, formerly Laminaria) is sometimes called haidai, to distinguish it from Ecklonia and other sources)
• Sargassum, a brown algae, as the source of haizao; Sargassum is a very large genus and several species seem to be in use.
• Porphyra, a red algae, as the source of zicai.
  
  

Saccharina and Sargassum have been used in China for the treatment of cancer. Inhibition of cancerous tumours in animals seems to be caused by long-chained polysaccharides. Dry Saccharina stipes have long been used in obstetrics to dilate the cervix and were known as "Laminaria tents"; the dry stipe slowly takes up water and expands; such stipes are also used in China for the insertion of intrauterine devices. According to Chinese medicine, seaweeds have a salty taste that is an indication that the material can disperse phlegm accumulation, particularly as it forms soft masses, include goitre, the thyroid swelling that indicates severe iodine deficiency.

The following are descriptions of seaweeds from Oriental Materia Medica:

Kunbu (Saccharina and Ecklonia) (Kombu in Japan)

• Essence and Flavor: Salty, Cold
• Channel Entered: Liver, Stomach, Kidney
• Actions: Softens hardness, disperses accumulation, resolves phlegm, cleanses heat
• Applications: Scrofula, goiter, tumor, edema, accumulation, testicular pain and swelling

 

Haizao (Sargassum) (Hiziki in Japan; generally Sargassum fusiforme, but other sargassi are used in China)

• Essence and Flavor: Bitter, Salty, Cold
• Channel Entered: Liver, Stomach, Kidney
• Actions: Disperses accumulated phlegm, disperses goiter and tumor, delivers water, cleanses heat
• Applications: Scrofula, goitre, tumor, edema, testicular pain and swelling

 

Zicai (Porphyra) (Nori in Japan)

• Essence and Flavor: Sweet, Salty, Cold
• Channel Entered: Lung
• Actions: Resolves phlegm, softens hardness, dispels heat, promotes diuresis
• Applications: Goiter, beriberi (leg swelling), edema, urinary infection, sore throat

The descriptions for kunbu and haizao are quite similar. Yang Yifan wrote about the differences between these commonly used seaweeds: Haizao and Kunbu are salty and cold, and enter the liver, lung, and kidney meridians. Both can clear heat, transform phlegm, soften hardness, and dissipate nodules. They can also promote urination and reduce edema. In clinical practice, they are often used together to treat nodules such as goiter and scrofula. There are some differences between the two seaweeds. Haizao is stronger in transforming phlegm and dissipating nodules, and it is more suitable for treating goiter and scrofula. Kunbu is stronger in softening hardness and reducing congealed blood; it is more suitable for treating liver-spleen enlargement, liver cirrhosis, and tumors. One of the best known formulas with the seaweeds is Haizao Yuhu Tang, or the Sargassum Decoction for the Jade Flask. This formula of 12 ingredients includes Sargassum, Ecklonia, and Saccharina. It was used to treat a condition of goitre which was so severe it made the throat look like a large flask. However, these seaweeds have been adopted into formulas for treating other soft swellings, including ovarian cysts, breast lumps, lymph node swellings, lipomas, and fat accumulation from simple obesity (modified from http://www.itmonline.org/arts/seaweed.htm).