Cetraria islandica is a lichen commonly called Iceland moss growing abundantly in the mountainous regions of northern countries including Iceland, Scotland, and northern England. It is also found in Arctic regions from Alaska to Newfoundland. In herbal medicine, Iceland moss is used to soothe and heal gut wall inflammation, and to treat chest infections, sore throat, cough, and bronchial asthma. It is known to consist of a considerable amount of polysaccharides, mainly lichenan and isolichenan. Lichenan is a β-glucan reported to have anti-viral and immunomodulatory activities. Protolichesterinic acid and fumarprotocetraric acid are also considered as major biologically active secondary metabolites found in Iceland moss.

Numerous scientific studies demonstrate its anti-oxidant, antimicrobial, and immunomodulating properties. Iceland moss found in high mountains and Arctic regions is generally exposed to strong UVB radiation. Lichens protect themselves from the radiation by maintaining high levels of screening pigments and melanins. Another study reported that salazinic acid, a compound found in Iceland moss, has a potential of UVA filter booster as well as anti-oxidant activity.