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 today for the treatment of pain (particularly low back pain and osteoarthritis), headache, and inflammatory conditions such as bursitis and tendinitis. The bark of white willow contains salicin, which is a chemical similar to aspirin (acetylsalicylic acid) and is thought to be responsible for the pain-reliving and anti-inflammatory effects of the herb. In fact, in the 1800s, salicin was used to develop aspirin. White willow appears to be slower than aspirin to achieve any effects, but those effects may last longer.

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 is used to ease pain and reduce inflammation, and there is good evidence that it is effective as an analgesic and anti-inflammatory. Researchers believe that the chemical salicin, found in willow bark, is responsible for these effects. However, studies have identified several other components of willow bark which have antioxidant, fever-reducing, antiseptic, and immune-boosting properties. Some studies have shown willow is as effective as aspirin for reducing pain and inflammation (but not fever), and at a much lower dose. Researchers theorize that may be due to the other compounds in the herb. More research is needed.

Treatment

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

Headache

Willow bark has been shown to relieve headaches and there is some evidence that it is less likely to cause the same gastrointestinal side effects that other pain relievers, such as ibuprofen and other nonsteroidal anti-inflammatory drugs, do. However, studies have not shown this conclusively, and people who are prone to stomach upset may want to avoid willow bark. Large-scale studies are needed to fully determine the safety and effectiveness of willow bark for chronic or recurrent headaches.

Low back pain

Willow bark appears to be effective for back pain. In a well-designed study of nearly 200 people with low back pain, those who received willow bark experienced a significant improvement in pain compared to those who received placebo. People 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

Several studies have shown that willow is more effective at reducing pain from osteoarthritis than placebo. 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 uses

Some professional herbalists may recommend willow bark for the following conditions, although at present, no scientific studies have supported these uses:

• Menstrual cramps
• Fever
• Flu
• Tendonitis
• Bursitis

Pediatric

Because of the danger of developing Reye syndrome (a rare but serious illness associated with the use of aspirin in children), children under the age of 16 should not be given willow bark.

Adult

General dosing guidelines for willow bark are as follows:

• Dried herb (used to make tea): boil 1 - 2 tsp of dried bark in 8 oz of water and simmer for 10 - 15 minutes; let steep for ½ hour; drink 3 - 4 cups daily
• Powdered herb (available in capsules) or liquid: 60 - 240 mg of standardized salicin per day; talk to your doctor before taking a higher dose
• Tincture (1:5, 30% alcohol): 4 - 6 mL three times per day

Because willow bark contains salicin, people who are allergic or sensitive to salicylates (such as aspirin) should not use willow bark. 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, take nonsteroidal anti-inflammatory drugs (NSAIDs) regularly or blood-thinning medication, be sure to consult your health care provider before taking willow bark. Willow bark should not given to children under the age of 16.

Side Effects

Side effects tend to be mild. However, 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).

Pregnancy and Breastfeeding

Salicylates are not recommended during pregnancy, so pregnant and breastfeeding women should not take willow bark.

Because willow bark contains salicylates, it has the potential to interact with a number of drugs and herbs. Talk to your doctor before taking willow bark if you take any other medications, herbs, or supplements.

Willow bark may interact with any of the following:

Anticoagulants (blood-thinning medications) -- Willow bark may strengthen the effects of drugs and herbs with blood-thinning properties.

Beta blockers -- including Atenolol (Tenormin), Metoprolol (Lopressor, Toprol-XL), Propranolol (Inderal, Inderal LA). Willow bark may reduce the effectiveness of these drugs.

Diuretics (water pills) -- Willow bark may reduce the effectiveness of these drugs.

Nonsteroidal anti-inflammatory drugs -- including ibuprofen (Advil, Motrin) and naproxen (Aleve). Taking willow bark with these drugs may increase risk of stomach bleeding.

Methotrexate and phenytoin (Dilantin) -- Willow may increase levels of these drugs in the body, resulting in toxic levels.

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