Educational information, not medical advice — ask your doctor or midwife.
Dog lichen is a leafy, grey-green lichen that grows on moss, soil and old walls. In Sweden and Norway it was called hundlav or grå åreskål. It was used in folk medicine, most famously against the bite of a mad dog.
A lichen is not one plant. It is a fungus living together with algae or bacteria. In dog lichen the partner is a cyanobacterium (a type of blue-green bacteria) called Nostoc.
That partner matters for safety. Some Nostoc strains make microcystins, which are toxins that can harm the liver. These have been found in Peltigera samples, in amounts nobody can predict.
There is no good human evidence that dog lichen treats any illness. Traditional use is not proof that a remedy works, and it is not proof that it is safe. This page gives no dose and no recipe, and the reasons are set out below.
Nobody knows how, or whether, dog lichen does anything in people. No human trial has tested it.
Lab work gives a few clues. In test tubes, lichen acids from Peltigera slow the growth of some bacteria. Whether that happens in a human body is not known.
In cell studies, compounds called tenuiorin and methyl gyrophorate block an enzyme (a working protein in cells) linked to swelling. That is a long way from a benefit you would feel.
The old rabies claim came from looks, not biology. Small root-like threads under the lichen reminded healers of dog teeth. Rabies is prevented by vaccine, and by nothing else.
Dog lichen is not a normal shop product. You will not find it on pharmacy shelves in most countries.
Where it does turn up, it is sold as:
- Dried whole lichen from foragers and craft sellers.
- Ground powder, sometimes inside mixed lichen blends.
- Rare tinctures (alcohol extracts) sold online.
None of these are standardised. No seller can tell you how much toxin a batch holds. Two bags from the same hillside can differ.
This page gives no home preparation method on purpose. Old teas and powders were made at the kitchen table, with no way to test them. Boiling does not reliably destroy microcystins.
Dog lichen was one of the best known folk remedies for the bite of a mad dog. Healers in Scandinavia and Britain used it against rabies for centuries. The idea came from the plant's shape, not from any test.
In 18th-century England it was mixed with black pepper and sold as a rabies powder. Scandinavian country medicine used hundlav for coughs, chest complaints and liver trouble. It was also laid on sores and used for mouth ulcers in children.
The rabies use faded as doctors learned how the disease works. Louis Pasteur's vaccine, from 1885, is why rabies deaths fell. The lichen had no part in that.
Records of the old uses are fairly good. Records of harm are poor. Folk users did not track liver damage, so quiet injury would not have been noticed.
Some reactions to Dog lichen need urgent care. Call your local emergency number or go to an emergency department straight away — do not wait to see whether it passes.
Go to an emergency department now if you were bitten, scratched or licked by an animal that might carry rabies. Do not wait for symptoms.
Get emergency care if you notice signs of liver injury:
- Yellow skin or yellow whites of the eyes
- Dark urine or pale stools
- Bad pain under the right ribs
- Repeated vomiting, confusion or extreme tiredness
Stop use and see your doctor for a spreading rash, swelling of the face or lips, or stomach upset that lasts. Tell them exactly what you took, and bring the packet or plant with you.
Dog lichen is not approved as a medicine in the EU, the UK or the United States. It is not an authorised herbal medicine and has no approved food use.
Picking lichens is also restricted in many Nordic nature reserves and national parks. Check local rules before gathering anything.
Do not swap one remedy for another on your own. Bring these options to your doctor or pharmacist and decide with them.
For a possible rabies exposure, the only answer is emergency care. Your doctor arranges vaccine and, if needed, rabies immune globulin. This is not a place for herbal choices.
For a cough, a pharmacist can suggest tested options such as simple honey-based syrups for adults and older children. They will also tell you when a cough needs a doctor.
For liver worries, ask your doctor for liver blood tests rather than self-treating. For mouth ulcers or slow-healing wounds, your pharmacist or practice nurse can recommend products with a known safety record.
Graded pages for the options named above:
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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