Iceland Moss

Metadata

Important taxonomic note: Despite its common name, Iceland Moss is not a moss (Bryophyta) nor a plant. It is a lichen — a composite organism formed by a symbiotic relationship between a fungus (mycobiont) and a photosynthetic alga or cyanobacterium (photobiont). The fungal partner provides the structural framework and absorbs water and minerals, while the algal partner performs photosynthesis. This dual nature means Iceland Moss cannot be classified under conventional botanical family systems in the same way as flowering plants. The family Parmeliaceae refers to the fungal component of the lichen.

Approved Indications

Commission E

• Approved: Loss of appetite (Appetitlosigkeit)
• Approved: Catarrh of the upper respiratory tract (Katarrhe der oberen Luftwege)

The Commission E monograph recognizes both the bitter tonic (appetite-stimulating) and demulcent (respiratory soothing) properties of Iceland Moss, reflecting its dual pharmacological character.

ESCOP

• No ESCOP monograph exists for Cetraria islandica

ESCOP has not issued a monograph on Iceland Moss, which represents a gap in the European evidence base rather than a negative assessment. This absence likely reflects the limited clinical trial data available for the herb.

EMA/HMPC

• Traditional use: Relief of irritation of the mucous membranes of the mouth and throat, and associated dry cough
• Traditional use: Temporary loss of appetite
• Classification is based on long-standing traditional use (not well-established use category)
• The HMPC concluded that although there is insufficient evidence from clinical trials, the effectiveness is plausible and there is evidence the herb has been used safely in this way for at least 30 years, including at least 15 years within the EU
• EMA monograph finalized November 2014 (EMA/HMPC/678891/2013)
• Age restriction for demulcent use: Adults, adolescents, and children over 6 years
• Age restriction for appetite loss: Adults only

Agreement/Disagreement Between Bodies

Commission E and EMA/HMPC are broadly aligned. Both recognize the dual indication for respiratory catarrh/dry cough (demulcent use) and appetite loss (bitter tonic use). The EMA is more specific in its wording, describing “irritation of the mucous membranes of the mouth and throat and associated dry cough” rather than Commission E’s broader “catarrh of the upper respiratory tract.” ESCOP’s absence is notable but does not represent a disagreement — it simply has not evaluated the herb. All regulatory assessments rest on traditional use evidence rather than clinical trial data, and neither body grants well-established use status.

Conditions Treated

Primary

• Dry, irritative cough — the core traditional indication; demulcent mucilage soothes irritated respiratory mucosa
• Sore throat and pharyngeal irritation — local application of mucilaginous preparations (lozenges, teas) coats and protects the inflamed throat lining
• Oral mucosal irritation — EMA-recognized traditional use

Secondary

• Loss of appetite / anorexia — bitter lichen acids (especially fumarprotocetraric acid and cetraric acid) stimulate gastric secretion and appetite through the bitter taste reflex
• Mild digestive complaints — traditional use as a bitter tonic for dyspepsia

Traditional/Historical

Iceland Moss has a rich history in Nordic and Central European folk medicine extending well beyond its current regulatory indications:

• Tuberculosis and chronic lung disease — historically one of the most prominent uses in Scandinavian, Spanish, French, and Turkish folk medicine; Iceland Moss decoctions were a standard remedy for consumption (phthisis) from the 17th through 19th centuries
• Bronchitis and bronchial catarrh — a broader respiratory application extending beyond simple dry cough
• Gastric and duodenal ulcers — traditional use in Iceland for gastrointestinal ulceration
• Nutritional supplement during famine — in Iceland and Scandinavia, the lichen was mixed with flour to make bread, added to porridge, or boiled into soups during food scarcity; the polysaccharide content provided caloric value
• General debility and convalescence — used as a nourishing restorative food-medicine in Nordic countries
• Nephritis (Sweden), hemostatic agent (Turkey), diabetes (Sweden) — isolated folk uses documented but without modern substantiation

The 17th-century Danish physician Borrichius documented that Danish apothecaries were already familiar with Iceland Moss by 1673. In 1683, Hiarne spoke favorably of its effects in hemoptysis and phthisis. The medieval botanist Valerius Cordus provided the earliest known botanical description, and the first published illustration with the notation “Muscus Eryngii folio” was produced by Breyne in 1672. Iceland Moss has been included continuously in European pharmacopoeias since the 1600s.

Mechanism of Action

1. Demulcent / Mucoprotective (Polysaccharides — Primary Mechanism)

The therapeutic core of Iceland Moss for respiratory indications lies in its high polysaccharide content (approximately 50% of dry weight), dominated by lichenin and isolichenin:

• Lichenin (beta-1,3/1,4-D-glucan) is a water-soluble polysaccharide that swells in hot water to form a viscous mucilaginous gel
• Isolichenin (alpha-1,3/1,4-D-glucan) contributes additional mucilage-forming capacity
• When ingested as a tea, lozenge, or syrup, these polysaccharides dissolve and form a protective film over irritated mucous membranes of the mouth, pharynx, and upper respiratory tract
• This bioadhesive film:
  • Shields exposed sensory nerve endings from mechanical and chemical irritation
  • Reduces the cough reflex by diminishing afferent stimulation of irritated mucosa
  • Provides a moist barrier promoting natural mucosal healing
  • Offers mild protection against secondary microbial invasion
• The mechanism is local and physical, not systemic — no absorption is required
• Onset of effect is rapid upon mucosal contact, similar to marshmallow (Althaea officinalis)

2. Bitter Tonic / Appetite Stimulation (Lichen Acids)

• Fumarprotocetraric acid (2.6—11.5% of dry weight) and cetraric acid are intensely bitter-tasting depsidones
• These bitter compounds activate taste receptors on the tongue, triggering a reflex increase in salivary and gastric secretion
• This reflex stimulation of digestive juices underlies the traditional and Commission E-approved use for loss of appetite
• The bitter component is so strong that traditional Scandinavian preparations sometimes involved pre-soaking the lichen in water with potassium carbonate to leach out bitter acids before culinary use
• For medicinal appetite stimulation, the full bitter extract (without pre-soaking) is preferred

3. Antimicrobial Activity (Usnic Acid and Other Lichen Acids)

• Usnic acid is a well-studied dibenzofuran derivative unique to lichens with documented antimicrobial activity
• Mechanism: primarily through inhibition of RNA and DNA synthesis in Gram-positive bacteria, with additional disruption of oxidative phosphorylation in microbial mitochondria
• In vitro activity demonstrated against Staphylococcus aureus, Bacillus species, Streptococcus species, and Mycobacterium species
• Methanol extracts of C. islandica also show activity against Gram-negative bacteria (E. coli, Proteus mirabilis) and fungi (Candida albicans, Aspergillus flavus)
• Protolichesterinic acid demonstrates in vitro activity against Helicobacter pylori (MIC 16—64 micrograms/mL across 35 strains) and Trypanosoma brucei (MIC 12.5 micromolar)
• Clinical relevance: Usnic acid content in Iceland Moss is very low (~0.04%), and it is questionable whether antimicrobial concentrations are achieved at therapeutic oral doses. The antimicrobial activity is considered a secondary or supporting property rather than a primary mechanism

4. Immunomodulatory Activity (Polysaccharides)

Preclinical research has identified immunomodulatory effects of Iceland Moss polysaccharides:

• Aqueous extract and purified lichenan modulate dendritic cell maturation in vitro, shifting the cytokine profile from IL-12p40 toward IL-10 (suggesting anti-inflammatory polarization)
• In vivo (rat model): aqueous extract administered subcutaneously significantly reduced BSA-induced arthritis, measured by decreased joint diameter
• Lichenan specifically reproduced this anti-inflammatory effect, while isolichenan and low-molecular-weight secondary metabolites were inactive
• In vivo carbon clearance test: aqueous extract increased the rate of colloidal carbon elimination by 1.1 to 1.5-fold, suggesting stimulation of reticuloendothelial phagocytic activity
• [Source: Freysdottir et al. 2008, International Immunopharmacology 8(3):423-430]

5. Antioxidant Activity

• Aqueous extract demonstrates 96—100% inhibition of lipid peroxidation of linoleic acid in vitro
• Higher antioxidant activity than alpha-tocopherol reported in some assays
• In vivo (streptozotocin-induced diabetic rats): increased SOD, CAT, and GPx enzyme activities; decreased MDA levels
• [Source: Gulcin et al. 2002, PubMed 11849836]

Key Active Constituents Summary

Clinical Evidence Summary

Clinical Trial Evidence

The clinical evidence base for Iceland Moss is extremely thin. This is one of the weakest evidence profiles among herbs with Commission E or EMA approval.

Kempe et al. (1997) — Post-Surgical Lozenge Study

• Design: Non-randomized, non-placebo-controlled study comparing three concentrations of Iceland Moss in lozenges
• Population: 61 patients who had recently undergone nasal septum surgery and were experiencing oral dryness and mucosal inflammation from obligate mouth-breathing
• Duration: 5 days post-operatively
• Results: Treatment with Iceland Moss lozenges produced “a direct reduction of the observed pathological changes” in mucosal coating, dryness, and inflammation. No significant differences emerged between the three concentration groups.
• Dose finding: 0.48 g per day (10 Isla-Moos lozenges per day) was determined to be a sufficient treatment dose
• Conclusion: Authors identified Iceland Moss as “an advisable therapeutic opportunity without interactions and side effects”
• Limitations: No placebo control, no randomization, small sample, specialized post-surgical population limits generalizability to typical upper respiratory irritation
• [Source: Kempe C et al. Laryngorhinootologie. 1997;76(3):186-188. PubMed 9213408]

This is the only identified clinical study specifically testing Iceland Moss preparations in humans for a respiratory/mucosal indication. No randomized, placebo-controlled clinical trials (RCTs) have been conducted for any indication.

Preclinical/In Vitro Evidence

Although clinical trials are absent, a moderate body of preclinical research supports pharmacological plausibility:

Immunomodulatory effects (Freysdottir et al. 2008)

• In vitro: Aqueous extract and lichenan modulated dendritic cell maturation, shifting cytokine balance toward anti-inflammatory IL-10
• In vivo: Significant reduction of BSA-induced arthritis in rats treated with aqueous extract
• Lichenan specifically drove the anti-inflammatory effect
• [Source: International Immunopharmacology 8(3):423-430. PubMed 18279796]

Immunomodulatory polysaccharides (Ingolfsdottir et al. 1994; Olafsdottir & Ingolfsdottir 2001)

• Polysaccharide fractions increased granulocytic phagocytosis and modulated complement-induced hemolysis
• Carbon clearance assay showed increased reticuloendothelial phagocytic activity in vivo
• [Source: PubMed 7809205; Planta Medica 67:768-769]

Antioxidant activity (Gulcin et al. 2002)

• Aqueous extract showed strong antioxidant activity (96—100% inhibition of linoleic acid peroxidation)
• [Source: PubMed 11849836]

Anti-Helicobacter pylori activity (Ingolfsdottir et al. 1997)

• Protolichesterinic acid showed in vitro activity against 35 strains of H. pylori (MIC 16—64 micrograms/mL)
• [Source: Antimicrobial Agents and Chemotherapy 41(1):215-217. PubMed 8980785]

Anticancer/antiproliferative activity

• Protolichesterinic acid showed dose-dependent cytotoxicity against breast cancer (T-47D, ZR-75-1) and erythroleukaemia (K-562) cell lines
• Reduced LRRC8A expression in A549 lung cancer cells
• Methanol extract cytotoxic against HepG2 (IC50 19.5 micrograms/mL), FemX melanoma (IC50 22.6 micrograms/mL), and LS174 colon carcinoma (IC50 33.7 micrograms/mL)
• [Source: PubMed 26549524; PMC 4158017]

Neuroprotective activity of fumarprotocetraric acid (Fernandez-Moriano et al. 2017)

• Increased cell survival and GSH/GSSG ratio in neuroblastoma and astrocyte cell lines
• Decreased lipid peroxidation, ROS, and caspase-3 activation
• Activated the Nrf2 antioxidant pathway
• [Source: PubMed 28041784]

Clinical Evidence Gaps

The evidence gaps are substantial:

• No RCTs exist for any indication (dry cough, sore throat, appetite loss)
• The single clinical study (Kempe et al. 1997) was non-randomized, non-blinded, and conducted in a post-surgical population
• No dose-response studies in human populations for the standard respiratory indications
• No head-to-head comparisons with other demulcent herbs (marshmallow, plantain) or with placebo
• No pharmacokinetic studies in humans
• Immunomodulatory and anticancer findings are entirely preclinical and not translatable to clinical claims
• The Commission E and EMA approvals rest almost entirely on traditional use documentation and pharmacological plausibility from in vitro/animal data

Evidence Assessment

Iceland Moss has a plausible pharmacological rationale: its high mucilage content would be expected to provide local demulcent relief analogous to better-studied herbs like marshmallow. The bitter acid content provides a rational basis for appetite stimulation. However, modern clinical evidence is virtually absent. The gap between centuries of traditional use and modern evidence-based standards is wider for Iceland Moss than for most herbs in this collection. The D rating reflects this disparity.

European vs US/Anglophone Consensus

Notable observation: Iceland Moss remains far more relevant in Germanic and Scandinavian pharmacy than in Anglophone herbal practice. Products like Isla-Moos (Engelhard Arzneimittel) are familiar OTC remedies in German-speaking countries, while the herb is virtually unknown to most American or British consumers.

Safety Profile

Contraindications

• Hypersensitivity to Cetraria islandica or other lichen species
• Gastric or duodenal ulcers — the bitter lichen acids may irritate the gastrointestinal mucosa and stimulate gastric acid secretion, which could worsen existing ulceration
• Not recommended for children under 6 years of age for cough/throat indications (EMA)
• Not recommended for children for appetite loss indications; adults only (EMA)

Drug Interactions

• No known drug interactions have been documented
• Theoretically, the high mucilage content could delay or reduce absorption of co-administered oral medications (analogous to the interaction noted for marshmallow and psyllium), though this has not been clinically demonstrated for Iceland Moss
• Practical precaution: take Iceland Moss preparations 30—60 minutes apart from other medications as a general measure

Adverse Effects

• No side effects have been reported at recommended therapeutic doses in the EMA assessment
• At high doses or with prolonged excessive use: nausea, loose stools, stomach irritation reported anecdotally
• Hepatotoxicity has been associated with isolated usnic acid in weight-loss supplements (notably the product LipoKinetix), but this is not relevant to traditional Iceland Moss preparations where usnic acid content is negligible (~0.04%) and embedded in a complex matrix
• Overall safety profile is excellent at traditional doses

Environmental Contamination Concern

• Lichens are efficient bioaccumulators of environmental pollutants, including heavy metals (lead, cadmium, mercury, chromium) and radioactive isotopes (e.g., cesium-137 after Chernobyl)
• Iceland Moss is listed in the European Food Safety Authority’s “Compendium of botanicals of possible concern” partly due to contamination potential
• Traditional decoction preparation significantly reduces elemental contamination to favorable health levels
• Quality-controlled commercial products from reputable European manufacturers are tested for contaminant levels and are considered safe
• This concern is more relevant for wild-harvested material from unknown sources

Pregnancy and Lactation

• Pregnancy: Not recommended due to insufficient safety data. No formal reproductive toxicity studies exist. The potential for environmental contaminant accumulation (particularly lead) adds a precautionary concern during pregnancy.
• Lactation: Not recommended due to insufficient safety data (EMA position)
• No traditional reports of harm during pregnancy or lactation have been identified, but the absence of safety data precludes a recommendation for use

Pediatric Use

• EMA permits traditional use in children over 6 years of age for cough and throat irritation
• Not recommended under 6 years due to insufficient data
• Appetite loss indication restricted to adults

Clinical Dosage

Herbal Tea / Decoction

Other Preparations

Preparation Notes

• For cough and sore throat: Hot infusion or decoction is preferred; drink slowly to maximize mucosal contact. Lozenges are an excellent delivery form for pharyngeal indications because they provide prolonged local contact.
• For appetite stimulation: The full bitter extract is required (do NOT pre-soak to remove bitter acids). Drink 30 minutes before meals.
• Bitter removal for culinary use: Historically, the thallus was soaked in water with potassium carbonate or wood ash to leach out the intensely bitter lichen acids before use as a food ingredient. This removes the appetite-stimulating properties but retains the mucilaginous nutritional value.
• Straining: Always strain decoctions through cloth or fine filter to remove any gritty particulate matter.

Duration

• Acute use for cough/sore throat: up to 1 week
• If symptoms persist beyond 1 week, medical consultation is recommended (EMA)
• For appetite loss: short-term use; consult a healthcare provider if appetite does not return

Sources

• German Commission E Monograph: Lichen islandicus (Cetraria islandica)
• EMA/HMPC Final European Union Herbal Monograph on Cetraria islandica (L.) Acharius s.l., thallus (EMA/HMPC/678891/2013, November 2014)
• EMA/HMPC Final Assessment Report on Cetraria islandica (L.) Acharius s.l., thallus (EMA/HMPC/36866/2014, November 2014)
• Kempe C, Gruning H, Stasche N, Hormann K. Icelandic moss lozenges in the prevention or treatment of oral mucosa irritation and dried out throat mucosa. Laryngorhinootologie. 1997;76(3):186-188. PubMed 9213408.
• Freysdottir J, Omarsdottir S, Ingolfsdottir K, Vikingsson A, Olafsdottir ES. In vitro and in vivo immunomodulating effects of traditionally prepared extract and purified compounds from Cetraria islandica. International Immunopharmacology. 2008;8(3):423-430. PubMed 18279796.
• Ingolfsdottir K. Molecules of interest: usnic acid. Phytochemistry. 2002;61(7):729-736.
• Ingolfsdottir K, Hjalmarsdottir MA, Sigurdsson A, Gudjonsdottir GA, Brynjolfsdottir A, Steingrimsson O. In vitro susceptibility of Helicobacter pylori to protolichesterinic acid from the lichen Cetraria islandica. Antimicrobial Agents and Chemotherapy. 1997;41(1):215-217. PubMed 8980785.
• Olafsdottir ES, Ingolfsdottir K. Polysaccharides from lichens: structural characteristics and biological activity. Planta Medica. 2001;67(3):199-208.
• Fernandez-Moriano C, Divakar PK, Crespo A, Gomez-Serranillos MP. In vitro neuroprotective potential of lichen metabolite fumarprotocetraric acid via intracellular redox modulation. Toxicology and Applied Pharmacology. 2017;315:83-97. PubMed 28041784.
• Gulcin I, Oktay M, Kufrevioglu OI, Aslan A. Determination of antioxidant activity of lichen Cetraria islandica (L) Ach. Journal of Ethnopharmacology. 2002;79(3):325-329. PubMed 11849836.
• Studzinska-Sroka E, Galanty A, Bylka W. The Genus Cetraria s. str. — A Review of Its Botany, Phytochemistry, Traditional Uses and Pharmacology. Molecules. 2022;27(15):4990. PMC 9370490.
• European Pharmacopoeia: Lichen islandicus monograph
• Wichtl M (ed). Herbal Drugs and Phytopharmaceuticals. 3rd ed. Stuttgart: Medpharm; 2004.
• Arzneipflanzenlexikon: Cetraria islandica (arzneipflanzenlexikon.info)
• WebMD: Iceland Moss overview

Connections

• Compare demulcent mechanism with Marshmallow (Althaea officinalis — higher mucilage content at 5—25%, stronger clinical evidence base, cold maceration preferred)
• Compare with Mullein (Verbascum densiflorum — also D-rated, similar reliance on traditional use; lower mucilage content at ~3% but adds saponin-based expectorant action)
• Plantain (Plantago lanceolata) shares the mucilage-based demulcent approach for respiratory indications
• Key distinction from Thyme and Ivy Leaf: Iceland Moss is for dry, irritative cough (demulcent), while thyme and ivy leaf target productive cough (secretolytic/expectorant). They address opposite ends of the cough spectrum.
• The bitter tonic / appetite-stimulating property connects Iceland Moss conceptually to Gentian, though through different bitter compounds (lichen acids vs. secoiridoid glycosides)
• Iceland Moss is commonly combined with Thyme and hyssop in European cough preparations, pairing the demulcent action with thyme’s antimicrobial and secretolytic properties