Educational information, not medical advice — ask your doctor or midwife.
Crottle rock lichen is a grey-green lichen that grows flat on bare rock. Its scientific name is Parmelia saxatilis. In Swedish it is called stenlav or bergsaltlav.
A lichen is not a plant. It is a fungus and an alga living as one body. This one forms crusty, leafy patches on boulders, stone walls and old roofs across northern Europe.
Its main historic job was dye, not medicine. Boiled with wool, it gives rust, brown and reddish shades. Folk use as a remedy was small and local.
Here is the honest verdict. There are no human trials of this lichen for any health problem. Long traditional use is not proof that something works, and it is not proof that it is safe.
No one has shown what this lichen does inside the human body.
Lichens make bitter defence chemicals known as lichen acids. In test tubes, several of these slow the growth of some bacteria and fungi. Some also mop up free radicals in lab dishes.
That is a long way from a health effect. A compound that kills bacteria in a dish may never reach skin or gut in a useful amount.
Related lichen acids, such as usnic acid from other species, have been studied in cells and animals. At higher amounts they can damage liver cells. That is a warning sign, not a benefit.
Some traditional uses may owe more to the method than the lichen. A warm wash cleans a graze. A steamy drink soothes a throat.
Neither needs lichen acids to feel better.
Most crottle sold today is craft material, not medicine.
- Dried whole lichen, sold for natural dyeing of wool and yarn. - Coarse powder, again mainly for dye baths. - Rare tinctures or extracts from small herbal makers.
You may also see capsules labelled broadly as "lichen extract". These often come from other species.
There is no standard medicinal preparation and no agreed strength. Two bags of the same weight can differ a lot in chemistry.
Wild-picked material is common. That carries the extra problem of correct naming, since several grey rock lichens look much alike.
In Scandinavia and the Scottish islands, crottle was valued chiefly as a dye.
Dyers boiled the lichen with wool to get warm brown and rust tones. The colour was used in homespun cloth and in tweed. Scrapers and simple hand tools for lifting it off rock are known from folk collections.
Medicinal use was a side note. Nordic and Gaelic folk records mention lichen washes for grazes and sore feet. Bitter lichen drinks were sometimes taken for coughs during hard winters.
Other lichens carried the larger food and medicine role. Iceland moss and reindeer lichen were the famine foods and the chest remedies. Crottle sat mostly in the dye pot.
These accounts describe what people did in the past. They are not a reason to try it now.
Stop using it and get medical help the same day if you notice signs of liver trouble. These are yellow skin or eyes, dark urine, pale stools, pain under the right ribs, or deep tiredness with nausea.
See a doctor promptly for a spreading rash, blisters or weeping skin after contact.
Call emergency services for swelling of the face, lips or tongue, or for trouble breathing.
Also see a doctor if a wound you have been washing with it looks redder, hotter or more painful, or starts to leak pus.
In the EU and the Nordic countries, crottle rock lichen is not licensed as a medicine. It is sold as dye and craft material, and as a food ingredient it would count as a novel food needing approval first.
Picking matters too. In Sweden and Norway, the right of public access covers berries, mushrooms and wildflowers, but not moss and lichen taken from someone else's land.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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