Grey alder (bark)

What is Grey alder (bark)?

Grey alder is a small, fast-growing tree of northern Europe, known in the Nordic countries as gråal, gråor or harmaaleppä. The part used in folk medicine is the bark, taken from young branches or trunks. Its botanical name is Alnus incana.

The bark tastes bitter and makes the mouth feel dry and tight. That drying feel comes from tannins, plant compounds that bind to proteins in tissue. Nordic households used it mostly as a mouth rinse, a wash for sore skin, and a tea for loose stools.

The honest verdict on evidence is simple. There are no good human trials of grey alder bark for any health use. Long standing in tradition is not proof that a remedy works, and it is not proof that it is safe.

Most of what is known comes from test tube and animal work on alder species. That kind of work can show what a plant does to cells. It cannot tell you what it will do in your body.

How does Grey alder (bark) work?

The main proposed action is astringency. Tannins bind proteins and make the surface of tissue feel tighter and drier. That chemical effect is real and easy to see in test tubes.

Whether it helps a sore throat, a graze or short-term diarrhoea in people has not been tested in trials. Tradition assumed it did. The link from "dries tissue" to "treats illness" is an assumption, not a finding.

In laboratory tests, extracts from alder bark slow the growth of some bacteria and fungi. In cell studies they also soak up free radicals, which are unstable molecules that can damage cells. Neither result has been repeated on human skin or in the human gut.

Alder barks also contain diarylheptanoids, a group of plant compounds studied for effects on inflammation in animals. Animal results often do not carry over to people. Treat the whole mechanism as a reasonable idea that nobody has confirmed in humans.

What forms does Grey alder (bark) come in?

Grey alder bark is sold and used in a few simple forms.

Dried, cut or shredded bark is the most common. It is simmered in water to make a decoction, which is a strong tea made by boiling rather than steeping.

Tinctures are liquid extracts made with alcohol. A few small Nordic herb suppliers offer them. Powdered bark in capsules is uncommon.

The bark is also sold for craft use rather than health use. It is a traditional dye for wool and a tanning agent for leather. Dye-grade bark is not prepared for anything you would swallow.

You will not usually find grey alder bark in mainstream pharmacies or large supplement brands. Most supply is from foragers and small herb shops in Finland, Sweden and Norway.

Where it comes from:

Grey alder bark had a steady place in Nordic folk medicine, especially in Finland and northern Sweden. Records from the 18th and 19th centuries describe it as a drying, binding remedy.

The bark was boiled and the liquid used to rinse the mouth for sore gums and mouth ulcers. It was also used as a wash for scrapes, rashes and sore feet. A weaker tea was given for short bouts of diarrhoea.

Sami and Finnish sources also mention chewing fresh inner bark for toothache and mouth pain. Alder bark was valued for tanning and dyeing at the same time. The same tannins did both jobs.

These accounts describe what people did in the past. They are not a recommendation to repeat it at home today, and they were written before anyone tested the plant properly.

What does Grey alder (bark) help with?

• Sore gums and mouth irritation (as a rinse): This is the best documented traditional use. A cooled bark decoction was swished in the mouth for sore gums and mouth ulcers. Tannins do make mouth tissue feel tighter straight away. That feel is real. Whether it speeds healing has not been tested in people. Strong tannin rinses can stain teeth over time and may irritate an already raw mouth.
• Sore throat (as a gargle): Tradition used the same decoction as a gargle for a rough, scratchy throat. There are no trials of grey alder bark for sore throat. Salt water and simple pain relievers have better support and are easier to judge. A sore throat with high fever, a rash, or trouble swallowing needs a doctor, not a herbal gargle.
• Minor grazes and skin irritation (as a wash): Folk practice used cooled bark liquid to wash scrapes, weeping rashes and sore feet. In laboratory tests, alder bark extracts slow the growth of some bacteria. Nobody has shown that this happens on human skin. Home-made plant washes are not sterile. Deep, dirty or spreading wounds need proper medical cleaning and sometimes antibiotics.
• Short bouts of diarrhoea: Weak bark tea was a household answer to loose stools across the Nordic countries. Tannin-rich plants are used this way worldwide. Even so, there are no controlled human trials of grey alder bark for diarrhoea. Any benefit is unproven. Rehydration matters far more than any herb. Diarrhoea with blood, black stools, high fever or signs of dehydration needs medical care.
• General 'drying' or binding use in folk practice: Older Nordic sources list alder bark among the binding or drying remedies, used for weeping sores and sweaty feet. This reflects how the plant feels, not a tested health effect. No modern study supports a general drying action in the body. Treat this use as historical background only.

What are the side effects of Grey alder (bark)?

• Nausea or stomach ache, especially on an empty stomach
• Vomiting after strong preparations
• Constipation
• Reduced iron absorption with repeated use
• Dark staining of teeth or tongue from rinses
• Mouth or throat irritation from strong decoctions
• Allergic reaction in people sensitive to alder or birch pollen

Good to know:

Most reported effects are mild and come from tradition and from what is known about tannins, not from trials.

Stomach upset is the most likely problem, and it tends to settle when you stop. Allergy is less common but more serious, since alder belongs to the birch family.

Stop and seek care if you get a rash, swelling of the lips or face, or any trouble breathing.

How much Grey alder (bark) should you take?

• Recommended daily: There is no established dose for grey alder bark. It is not a standard supplement, so most supplies carry no health label at all. Where tannin-rich barks are sold as tea in Europe, labels often sit near 1 to 2 grams of dried bark per cup. That is a label norm for this type of plant, not a recommendation for you. Strength varies a lot between batches, which makes any number rough at best. If you are thinking about using it, ask a pharmacist or doctor first, especially if you take any medicine.
• Best time of day: Time of day does not seem to matter for this plant. One timing point does matter. Tannins bind iron and some medicines in the gut, so spacing is more useful than clock time. Keeping it a few hours away from iron tablets and prescription medicines is the usual pharmacy advice for tannin-rich teas.
• With or without food: Taking strong bark tea on an empty stomach can cause nausea. Food usually softens that. There is a trade-off. Tannins taken with a meal can cut how much iron your body absorbs from that meal. If you are low in iron or treating anaemia (low iron), keeping tannin-rich drinks away from meals and iron tablets is the safer habit.
• Time to effect: As a mouth rinse, the drying, tightening feel is immediate. That is a taste and touch effect, not proof of healing. For diarrhoea or skin use, no reliable time frame exists, because the effect itself is unproven. It is fair to expect that it may do nothing for your symptoms. If nothing changes in a day or two, stop and get advice.
• How long to take it: Traditional use was short. Bark teas and rinses were used for a few days around a specific problem. No one has studied what happens with daily use over weeks or months. Heavy, long-term tannin intake has been linked to liver and gut strain in animal work. A symptom that is not settling within a couple of days is a reason to see a doctor, not to keep going.