The use of willow bark dates back to the time of Hippocrates (400 BC) when patients were advised to chew on the bark to reduce fever and inflammation. Willow bark has been used throughout the centuries in China and Europe, and continues to be used by herbalists today for the treatment of fever, pain (particularly low back pain), headache, and inflammatory conditions such as arthritis. Although the bark of the white willow is most commonly used medicinally, the bark of related species, such as black willow, have been shown to have the same beneficial effects.

The willow family includes a number of different species of deciduous trees and shrubs native to Europe, Asia, and some parts of North America. Some of the more commonly known are white willow/European willow (Salix alba), black willow/pussy willow ( Salix nigra), crack willow (Salix fragilis), purple willow (Salix purpurea), and weeping willow (Salix babylonica). The willow bark sold in Europe and the United States usually includes a combination of the bark from white, purple, and crack willows.

Willow bark's most important medicinal qualities are its ability to ease pain and reduce inflammation. In fact, it was from salicylic acid, one of the ingredients in willow bark, that aspirin was originally synthesized. Studies have identified several other components of willow bark which have antioxidant, fever-reducing, antiseptic, and immune-boosting effects.

Studies suggest that willow bark may be useful for the following conditions:

Headache
Willow bark has been shown to relieve headaches and some experts suggest that it may be preferable to certain conventional therapies such as ibuprofen and other non-steroidal anti-inflammatories, which have been linked to serious gastrointestinal side effects. Large-scale studies are necessary to fully determine the safety and effectiveness of willow bark for chronic or recurrent headaches, however.

Low Back Pain
In a study of nearly 200 people with low back pain, participants who received willow bark experienced a significant improvement in pain compared to those who received placebo. Moreover, participants who received higher doses of willow bark (240 mg salicin) had more significant pain relief than those who received low doses (120 mg salicin).

Osteoarthritis
In a small study of people with osteoarthritis of the neck or lower back, those who received willow bark experienced significant improvement in symptoms compared to those who received placebo. A similar study of 78 patients hospitalized with osteoarthritis of the knee or hip joint found that patients who received willow bark experienced significant pain relief compared to those who received placebo.

Other Conditions
Some professional herbalists may recommend willow bark for the following conditions, although at present, no scientific studies have been conducted to support these uses:

• Sexual dysfunction
• Mild diarrhea with cramps
• Fever
• Flu
• Tendonitis
• Bursitis
• Ankylosing spondylitis (a form of rheumatoid arthritis affecting the lower spine)

The use of willow bark in children has not been evaluated in well-designed scientific studies. Some researchers speculate that the salicin in willow may increase the risk for Reye's syndrome (a serious condition that affects the liver and sometimes the brain and which is marked by recurrent vomiting). Although there is no documented evidence that the herb can cause such a serious condition, it is recommended that willow bark not be used by children with flu-like symptoms, chickenpox, fever, or dehydration until conclusive evidence shows that there is no risk.

General dosing guidelines for willow bark are as follows:

• Dried herb (used to make tea): boil 1 to 2 tsp of dried bark in 8 oz of water and simmer for 10 to 15 minutes; let steep for ½ hour; drink 3 to 4 cups daily
• Powdered herb (available in capsules): 1 to 3 g daily
• Tincture (1:5, 30% alcohol): 4 to 6 mL three times per day
• Standardized extract: tablets or liquid containing 60 to 240 mg of salicin once a day

Because willow bark contains salicin, people who are allergic or sensitive to salicylates (such as aspirin) should not use willow bark. Although the scientific evidence is inconclusive, some researchers suggest that people with asthma, diabetes, gout, gastritis, hemophilia, and stomach ulcers should also avoid willow bark. If you have any of these conditions, be sure to consult your healthcare provider before taking willow bark.

There is no evidence of adverse effects associated with willow bark. However, side effects such as gastrointestinal irritation and ulcers are potentially associated with all compounds containing salicylates. Overdoses of willow bark may cause skin rash, stomach inflammation/irritation, nausea, vomiting, kidney inflammation, and tinnitus (ringing in the ears).

Salicyclates are not recommended during pregnancy, so it may be wise for pregnant and breastfeeding women to avoid willow bark.

Because willow bark contains salicylates, it has the potential to interact with blood-thinning medications, such as aspirin and warfarin. People who are taking anticoagulant or antiplatelet medications should avoid the use of willow bark althogether, except under strict medical supervision.

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