Quick Summary
Iceland Moss (Cetraria islandica) is a lichen known for its unique secondary metabolites with potential antimicrobial properties, particularly lichesterinic acid. It has been investigated mainly for its antimicrobial activity against resistant pathogens like MRSA, along with preliminary evidence suggesting immunomodulatory and wound healing effects. However, clinical evidence specifically for human therapeutic use is limited and research is still pending.
What is it?
Iceland Moss is a type of lichen commonly found in alpine and arctic regions. It produces distinctive secondary metabolites that contribute to its biological activity. Traditionally harvested for medicinal and nutritional purposes, it grows on soil and rocks and has a moss-like appearance, though it is not a true moss.
Traditional Uses
- Symptomatic management of mild upper respiratory tract infections (MURTIs)
- Support for respiratory health and soothing irritated mucous membranes
- Topical use to support wound healing and skin repair
These uses are rooted in traditional herbal medicine and integrative healthcare practices, although rigorous clinical validation is lacking.
Active Compounds
- Lichesterinic acid – a key secondary metabolite with antimicrobial effects
- γ-Propoxy-sulfo-lichenan – associated with keratinocyte differentiation
- Other lichen secondary metabolites with potential bioactivity
Potential Benefits with Evidence Levels
- Antimicrobial activity including activity against MRSA
Evidence level: Preclinical (in vitro, molecular docking, and animal toxicity studies)
Studies indicate lichesterinic acid isolated from C. islandica has antimicrobial effects against MRSA and other bacteria with minimum inhibitory concentrations (MIC) of 64-128 μg/mL. Synergistic effects with antibiotics and low toxicity in animal models have also been reported.
Unearthing anti-MRSA agents from alpine lichens (2025)
Unassuming Lichens: Nature’s Hidden Antimicrobial Warriors (2025) - Potential wound healing and keratinocyte differentiation support
Evidence level: Preclinical (in vitro cell studies)
γ-Propoxy-sulfo-lichenan derived from Iceland Moss has shown to induce human keratinocyte differentiation in vitro, suggesting potential for promoting wound healing.
γ-Propoxy-Sulfo-Lichenan Induces In Vitro Cell Differentiation of Human Keratinocytes (2019) - Use in symptomatic management of mild upper respiratory tract infections (MURTIs)
Evidence level: Traditional use / clinical guidance consensus
Iceland Moss is among herbs listed for symptomatic relief in mild URTIs based on traditional and integrative medicine approaches, though specific clinical trials are lacking.
Holistic care in mild upper respiratory tract infections (MURTIs) (2025)
Side Effects
No specific human clinical adverse effects have been documented or reported in the available studies. Hepatotoxicity associated with usnic acid, a metabolite found in some other lichen species, has not been observed with compounds isolated from Cetraria islandica.
Drug Interactions
No clinical data are available regarding drug interactions with Cetraria islandica or its isolated compounds. Caution is advised when combining with other medications until more information is available.
Who Should Avoid It
- Pregnant or breastfeeding individuals due to lack of safety data
- Those with known allergies to lichens or related species
- People advised by healthcare providers to avoid herbal supplements lacking clinical safety data
Evidence Limitations
- The majority of evidence is preclinical, including in vitro and animal studies; clinical data in humans are lacking.
- No randomized controlled trials or systematic reviews specifically assess human clinical efficacy.
- Traditional and integrative uses have not been validated through rigorous clinical research.
- Toxicology and safety profiles in humans remain unestablished; extrapolation from animal studies should be cautious.
- Potential hepatotoxicity reported with some related lichen metabolites (e.g., usnic acid) warrants careful evaluation.
- Variability in secondary metabolite content may occur due to source, cultivation, and extraction methods.
- No data on drug interactions or contraindications in humans.
- Safety during pregnancy and breastfeeding has not been investigated.
References
- Unearthing anti-MRSA agents from alpine lichens: discovery and characterization of bioactive compounds in Cetraria islandica from the snowy Cangshan region (2025). DOI: 10.3389/fmicb.2025.1688435
- Unassuming Lichens: Nature’s Hidden Antimicrobial Warriors (2025). DOI: 10.3390/ijms26073136
- γ-Propoxy-Sulfo-Lichenan Induces In Vitro Cell Differentiation of Human Keratinocytes (2019). DOI: 10.3390/molecules24030574
- Holistic care in mild upper respiratory tract infections (MURTIs): an approach to individualized care management (2025). DOI: 10.7573/dic.2025-7-12
- Bioactive Lichen Secondary Metabolites and Their Presence in Species from Chile (2023). DOI: 10.3390/metabo13070805
Last Reviewed
June 2024
Disclaimer: The information provided here is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before using any herbal products or supplements, especially if you are pregnant, breastfeeding, have underlying health conditions, or are taking other medications.