Educational information, not medical advice — ask your doctor or midwife.
Willow is the dried bark of the white willow tree, Salix alba. It is sold as a herbal pain remedy, mostly for sore backs, joints and muscles. The bark contains salicin, a plant cousin of aspirin.
White willow grows across Europe and western Asia and was carried to North America. American folk healers and the Eclectic doctors of the 1800s used the bark for fever, aches and joint pain. Chemists studied that same bark on the road to making aspirin.
Here is the honest verdict on the evidence. A few small human trials point to modest relief in low back pain. Other trials found no benefit for arthritis, and the research is old, thin and mostly from one group.
Long traditional use is real. But tradition is not proof that a remedy works, and it is not proof that a remedy is safe.
Willow bark carries the same kinds of risks as aspirin. That shapes who can use it far more than the strength of the evidence does.
The main actor is salicin, a compound closely related to aspirin.
Your gut bacteria and your liver turn salicin into salicylic acid. Aspirin also breaks down into salicylic acid. That much is well established in people.
Salicylic acid blocks COX enzymes, the body proteins that make pain, swelling and fever signals. Most of that work comes from lab and animal studies rather than from people.
The salicin in a usual herbal dose is small next to a pain dose of aspirin. So some researchers think other parts of the bark add to the effect.
In test-tube work, the bark's polyphenols (plant compounds that act as antioxidants) also damp down inflammation signals. Whether that happens in your body is not established.
Small studies suggest willow bark affects platelets (the blood cells that form clots) less than aspirin does. Do not treat that as a safety clearance. If aspirin is risky for you, willow bark should be treated as risky too.
Willow bark is sold in several forms. Standardised dry extracts are the form used in most human trials.
The dry forms are:
- Dried shredded bark, brewed as a tea or decoction - Capsules and tablets of powdered bark - Standardised dry extracts, labelled by salicin content
You can also buy:
- Liquid tinctures in alcohol - Combination joint or back formulas, often mixed with other herbs
Loose bark and tinctures vary widely in strength. Topical willow creams exist, but human testing for them is very limited.
Willow bark has a long record in Western folk medicine. Writers in ancient Greece and Rome noted bark and leaf preparations for pain and fever.
In 19th-century America, folk healers and Eclectic physicians listed willow bark as a bitter tonic and fever remedy. It was also used for rheumatism, headache and period pain.
Chemists isolated salicin from willow in the early 1800s. That work fed into the development of salicylic acid and later aspirin. Once aspirin arrived, the bark largely fell out of medical use.
This history explains why willow is well known. It does not tell you that the bark works or that it is gentle.
Stop willow bark and get urgent medical help if you have black or tarry stools, vomit that looks like blood or coffee grounds, or severe stomach pain.
Get emergency help for wheeze, swelling of the face or lips, or a spreading rash. These can mean a salicylate allergy.
Stop and see your doctor if you get ringing in the ears, easy bruising, dark urine or much less urine than normal.
Also see a doctor if your pain has not improved after two weeks, or if pain follows an injury, comes with fever, or wakes you at night.
In the United States, willow bark is sold as a dietary supplement. It is not approved as a drug for any condition. In Germany, the Commission E monograph covers willow bark for pain and fever. In the United Kingdom, some products hold a Traditional Herbal Registration, which is based on long use rather than proof of effect.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
One email with the summary. We'll also send a short weekly evidence update — unsubscribe any time.
