The use of willow bark dates to the time of Hippocrates (400 BC) when people 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). In combination with the herb's powerful anti-inflammatory plant compounds (called flavonoids), salicin is thought to be responsible for the pain-relieving and anti-inflammatory effects of the herb. In fact, in the 1800s, salicin was used to develop aspirin. White willow appears to bring pain relief more slowly than aspirin, but its effects may last longer.
The willow family includes a number of different species of trees and shrubs native to Europe, Asia, and some parts of North America. Some of the more commonly known species 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). Not all willow species accumulate a therapeutically sufficient amount of salicin. In one study, the amount of salicin after 1 and 2 year growth in autumn and spring ranged from 0.08 to 12.6%. 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. Researchers believe that the chemical salicin, found in willow bark, is responsible for these effects. However, studies show several other components of willow bark, including plant chemicals called polyphenols and flavonoids, have antioxidant, fever-reducing, antiseptic, and immune-boosting properties. Some studies show willow is as effective as aspirin for reducing pain and inflammation (but not fever), and at a much lower dose. Scientists think that may be due to other compounds in the herb. More research is needed.
Studies suggest that willow bark may be useful for the following conditions:
Willow bark has been shown to relieve headaches. There is some evidence that it is less likely to cause gastrointestinal side effects than other pain relievers, such as ibuprofen (Advil) and other nonsteroidal anti-inflammatory drugs, do. However, studies have not shown this beyond all doubt, and people who are prone to stomach upset may want to avoid willow bark. Large-scale studies are needed to fully determine how safe and effective willow bark is for chronic or recurring 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).
Several studies show 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 people hospitalized with osteoarthritis of the knee or hip joint found that people who received willow bark had significant pain relief compared to those who received placebo.
Professional herbalists may recommend willow bark for the following conditions, however, more research is needed.
- Menstrual cramps
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 18 should not take willow bark.
Speak to your doctor to determine the appropriate dose for you.
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, stomach ulcers, or with kidney or liver issues should also avoid willow bark. If you have any of these conditions, or if you take nonsteroidal anti-inflammatory drugs (NSAIDs) or blood-thinning medication, ask your health care provider before taking willow bark. Children under the age of 16 should not take willow bark.
Side effects tend to be mild. However, stomach upset, ulcers, nausea, vomiting, and stomach bleeding are potential side effects of 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 might 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, and increase the risk of bleeding.
Beta blockers: including Atenolol (Tenormin), Metoprolol (Lopressor, Toprol-XL), Propranolol (Inderal, Inderal LA). Willow bark may make these drugs less effective.
Diuretics (water pills): Willow bark may make these drugs less effective.
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 bark may increase levels of these drugs in the body, resulting in toxic levels.
Bisset NG. Herbal Drugs and Phytopharmaceuticals. Stuttgart, Germany: Medpharm Scientific Publishers; 2004:534-536.
Blumenthal M. The Complete German Commission E Monographs. Austin, TX: American Botanical Council. Boston: Integrative Medicine Communications; 1998.
Chrubasik JE, Roufogalis BD, Chrubasik S. Evidence of effectiveness of herbal anti-inflammatory drugs in the treatment of painful osteoarthritis and chronic low back pain. Phytother Res. 2007 Jul;21(7):675-83. Review.
Chrubasik S. Pain therapy using herbal medicines [abstract]. Gynakologe. 2000;33(1):59-64.
Chrubasik S, Eisenburg E, Balan E, et al. Treatment of low back pain exacerbations with willow bark extract: a randomized double blind study. Am J Med. 2000;109:9-14.
Enayat S, Banerjee S. The ethanolic extract of bark from Salix aegyptiaca L. inhibits the metastatic potential and epithelial to mesenchymal transition of colon cancer cell lines. Nutr Cancer. 2014;66(6):999-1008.
Ernst E, Chrubasik S. Phyto-anti-inflammatories. A systematic review of randomized, placebo-controlled, double-blind trials. Rheum Dis Clin North Am. 2000;26(1):13-27.
Foster S, Duke JA. A Field Guide to Medicinal Plants and Herbs of the Eastern and Central US. Boston, MA: Houghton Mifflin; 2000:321-323.
Freischmidt A, Jurgenliemk G, Kraus B, et al. Contribution of flavonoids and catechol to the reduction of ICAM-1 expression in endothelial cells by a standardised Willow bark extract. Phytomedicine. 2012;19(3-4):245-52.
Gagnier JJ, van Tulder M, Berman B, Bombardier C. Herbal medicine for low back pain. Cochrane Database Syst Rev. 2006;(2):CD004504.
Heck AM, DeWitt BA, Lukes AL. Potential interactions between alternative therapies and warfarin. Am J Health Syst Pharm. 2000;57(13):1221-1227.
Hoffmann D. Therapeutic Herbalism. Santa Cruz, CA: Therapeutic Herbalism Press; 2000.
Kenstaviciene P, Nenortiene P, Kiliuviene G, Zevzikovas A, Lukosius A, Kazlauskiene D. Application of high-performance liquid chromatography for research of salicin in bark of different varieties of Salix. Medicina. 2009;45(8):644-51.
Kuhn MA, Winston D. Herbal Therapy and Supplements. Philadelphia, PA: Lippincott; 2001.
Little CV, Parsons T, Logan S. Herbal therapy for treating osteoarthritis. The Cochrane Library. 2002:1.
McGuffin M, Hobbs C, Upton R, et al, eds. American Herbal Products Association's Botanical Safety Handbook. Boca Raton, FL: CRC Press; 1997:101.
Rakel: Integrative Medicine. 3rd. ed. Philadelphia, PA: Elsevier Saunders; 2012.
Schmid B, Ludtke R, Selbmann HK, et al. Efficacy and tolerability of a standardized willow bark extract in patients with osteoarthritis: randomized placebo-controlled, double blind clinical trial.Phytother Res. 2001 Jun;15(4):344-50.
Setty AR, Sigal LH. Herbal medications commonly used in the practice of rheumatology: mechanisms of action, efficacy, and side effects. Semin Arthritis Rheum. 2005 Jun;34(6):773-84.
Uehleke B, Muller J, Stange R, Kelber O, Melzer J. Willow bark extract STW 33-I in the long-term treatment of outpatients with rheumatic pain mainly osteoarthritis or back pain. Phytomedicine. 2013;20(11):980-4.
Vlachojannis J, Magora F, Chrubasik S. Willow species and aspirin: different mechanism of actions. Phytother Res. 2011;25(7):1102-4.