What is Willow?

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.

How does Willow work?

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.

What forms does Willow come in?

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.

Where it comes from:

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.

What does Willow help with?

• Low back pain: This is the best-studied use, and the evidence is still modest. Two small trials of a high-salicin extract found better pain relief than placebo over four weeks. The trials were small, and later reviews rated the quality as low. Expect mild help at best, not a fix.
• Osteoarthritis joint pain: Tradition treated willow as a rheumatism remedy. Human results clash. One small trial found modest benefit in knee and hip osteoarthritis. A larger trial found no benefit over placebo. On balance, the evidence here does not support confident use.
• General muscle aches: Folk use for strains and overworked muscles is old and widespread. There are no good human trials for this specific use. Any benefit is assumed from the salicylate content rather than shown.
• Headache: Eclectic and folk sources listed willow for headache. No modern trial has tested willow bark for headache or migraine. The salicin dose in herbal products is well below an aspirin pain dose.
• Fever: Bringing down fever was a classic traditional use. Salicylates do lower fever in people, which makes the idea plausible. Willow bark itself has not been tested for fever in a proper trial. Fever in a child or teen is a reason to avoid willow entirely, not to try it.
• Period pain: Folk use for cramps exists but is less prominent. No human trial supports it. Standard anti-inflammatory painkillers have far better evidence here.

What are the side effects of Willow?

• Upset stomach, nausea or heartburn
• Stomach pain
• Diarrhoea or loose stools
• Skin rash or itching
• Allergic reaction, including wheeze in people sensitive to aspirin
• Ringing in the ears at high intake
• Stomach or gut bleeding (rare but serious)
• Kidney strain, mainly in people who already have kidney trouble

Good to know:

Most reported effects are mild and involve the stomach. They are more likely at higher amounts and with longer use.

The serious risks are the aspirin-type ones: gut bleeding, allergic reactions and kidney strain. These are uncommon, but they are real and can be severe.

People who react badly to aspirin can react badly to willow bark. Treat any wheeze, swelling or hives as an emergency.

How much Willow should you take?

• Recommended daily: Labels on standardised willow bark extracts commonly state a daily amount giving about 120 to 240 mg of salicin. Human trials have used that range. This is background information, not advice for you. The right amount, if any, depends on your health, your medicines and your age. Ask a pharmacist or doctor first.
• Best time of day: Timing is not critical. Many people split the amount across the day because pain relief does not last all day. Taking it late in the evening offers no known advantage.
• With or without food: Take it with food. Salicylates can irritate the stomach lining, and food lowers that irritation. Avoid taking it with alcohol, which adds to the stomach risk.
• Time to effect: Some people report mild relief within a few hours. In trials, the clearer differences showed up after one to two weeks of daily use. It may also do nothing for you. If there is no change after two weeks, further use is unlikely to help.
• How long to take it: Trials ran for about two to six weeks. Traditional use was short-term, for a flare rather than for years. Long-term daily use has not been studied for safety. Ongoing pain is a reason to get a diagnosis, not to keep dosing.