Educational information, not medical advice — ask your doctor or midwife.
Alnus rhombifolia is the white alder, a streamside tree of the western United States. It grows along rivers and creeks in California, Oregon and Nevada. The bark is the part most often named in folk use, with the leaves used less often.
In North American folk practice, alder bark was simmered into a wash or a bitter tea. People applied it to sores and skin irritation, or drank small amounts for loose bowels.
Traditional use shows that people valued the plant. It is not proof that it works, and it is not proof that it is safe.
Here is the honest verdict on evidence. There are no human trials of white alder for any health use. Most laboratory work has been done on related alders, such as red alder, not on this species.
That means every benefit you may read about is unproven in people. White alder is also not a food, and it is rarely sold as a finished herbal product. If you are weighing it up, treat it as a traditional plant with an open question mark, not a treatment.
No one has shown what white alder does in the human body. What follows is proposed, not proven.
Alder bark is rich in tannins. Tannins are plant compounds that bind protein and give a dry, puckering feel in the mouth. That astringent action is why bark washes were used on weeping sores and why bark teas were used for loose bowels.
In test tubes, tannins from various plants bind protein and slow some bacteria. Whether a bark wash does anything useful on human skin has not been tested.
Alders also contain diarylheptanoids, a group of compounds that includes oregonin. In cell and animal studies on related alder species, oregonin appears to lower markers of inflammation and mop up reactive molecules. These studies used extracts, not teas, and they were not done in people.
Fresh alder bark has a long-reported tendency to cause vomiting. Older accounts say the bark was dried or aged for months before use for this reason. The compounds behind that effect have not been clearly identified.
So the fair summary is this. There is a plausible chemical story. There is no human evidence that the story leads to a benefit you would notice.
White alder is not a mainstream herbal product. You are unlikely to find it in a pharmacy or a standard supplement range.
Where it is used at all, the usual forms are:
Dried bark, cut or shredded, simmered into a strong tea called a decoction.
A cooled bark decoction used as a skin wash or compress.
Tinctures, meaning alcohol extracts, made by small independent herb sellers.
Powdered bark, sold occasionally for craft dyeing rather than for health use.
Alder wood and chips are also sold for smoking food and for woodworking. Those are not health products and are not meant to be eaten.
Nothing sold as white alder is standardised. That means two products can differ a lot in strength, and neither will tell you how much of any compound you are getting. Mislabelling is a real risk too, because several alder species look alike and are often traded under loose common names.
White alder belongs to the folk plant knowledge of western North America, recorded mainly from the 1800s onward.
Several Indigenous peoples of California and the Pacific Northwest used alder barks. Recorded uses included washes for sores and skin trouble, teas for stomach and bowel complaints, and preparations for aches. Red alder and white alder were often used in similar ways where both grew.
Alder bark also had a strong non-medical role. It was a major source of red and brown dye for baskets, nets and hides. The wood was prized for smoking fish.
Written accounts of fresh bark note that it could cause vomiting. Practitioners reportedly dried or cured the bark before using it, which suggests the effect was well known.
These accounts describe what people did in the past. They are a record of practice, not a recommendation, and they do not tell you what is safe to do now.
Stop and see a doctor if you vomit repeatedly, get bad stomach pain, or notice blood in your stool.
Get urgent help for swelling of the lips, face or throat, a widespread rash, or trouble breathing. Those are signs of a serious allergic reaction.
See a doctor if a skin sore spreads, weeps or turns red and warm. That can mean infection.
See a doctor if diarrhoea lasts more than two days, or if you feel faint, tired or unusually short of breath, which can signal low iron.
White alder is not approved as a medicine in the United States, the United Kingdom or the European Union. If sold in the US it would fall under dietary supplement rules, which means it is not reviewed for safety or effect before sale. The tree itself is an unregulated native plant, though collecting bark on public or protected land may need permission.
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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