Willow bark is useful in relieving muscle and joint pain, but may have side effects similar to aspirin.
Willow bark is commonly used to treat pain and reduce fevers. It contains a compound called salicin that has been shown to have anti-inflammatory effects. Several studies have shown that willow bark extracts are effective in reducing back pain and osteoarthritis.
Although aspirin is developed from salicin, a direct comparison between aspirin benefits and willow bark benefits cannot be made. At the same time, aspirin-like side effects may occur with willow bark.
To reduce fever
Willow bark is thought to act in a similar way as aspirin, but clinical trials have not been performed.
To treat pain, including muscle and joint pain
Clinical trials have shown that willow bark extract is effective in treating low back pain. Other study results are mixed for its ability to relieve osteoarthritis pain.
To aid in weight loss
There are no studies to indicate that willow bark can aid in weight loss, and a case report of allergic reaction in someone who used a weight-loss product with willow bark.
Due to possible bleeding complications, willow bark should be discontinued before surgery or chemotherapy.
Individuals with impaired platelet function should also avoid willow bark, as it may interfere with blood clotting.
Do Not Take If
You are taking warfarin or other blood thinners: Willow bark may increase the risk of bleeding.
You are taking non-steroidal anti-inflammatory drugs (NSAIDs): Willow bark may increase the risk of stomach and intestinal damage and bleeding.
You have sensitivity to aspirin or aspirin-containing products.
You have asthma, breathing problems, chest tightness, or throat tightness.
You have stomach problems or an ulcer.
You are having skin rash, hives, or itchy / swollen skin.
Stomach or intestinal discomfort, allergic reaction, sudden rash, or itching
May prevent blood clotting or cause bleeding problems
Serious allergic reaction in a 25-year-old woman with a history of allergy to aspirin products. The product used was a supplement promoted for weight-loss that contained willow bark.
Acute breathing distress in a 61-year-old woman who suddenly became short of breath and coughed repeatedly after taking willow bark.
Children should not be given willow bark because of the potential for developing Reye syndrome, a serious condition associated with the use of aspirin.
Willow is a deciduous tree native to Europe, Asia and some parts of North America. Its bark has been used for thousands of years in China and Europe as a remedy for fevers and pain.
Willow bark extracts exert anti-inflammatory (1), antiplatelet (2), and antiproliferative (3) effects in vitro.
Clinical studies indicate that willow bark may help manage back pain (5)(6), although studies of osteoarthritis are mixed (7)(8)(9), and possibly negative for rheumatoid arthritis (6)(9). Topical application of salicin may help reduce skin aging (10).
In vitro and animal models suggest that salicin in willow bark has antitumor and antiangiogenic effects (4).
Aspirin, a drug derived from salicin, has been studied for the prevention of cardiovascular diseases as well as cancer (21). However, willow bark should not be used as a substitute for aspirin because of the variation in its potency. Children should not be given willow bark because of the potential for developing Reye syndrome, a serious condition associated with the use of aspirin (22).
Mechanism of Action
Although anti-inflammatory activity is mostly attributed to salicin (13), a main bioactive compound in willow bark, catechol and flavonoid compounds have also been found to be responsible (12). Willow bark inhibits pro-inflammatory cytokines (tumor necrosis factor [TNF]-alpha), cyclo-oxygenase (COX)-2, and nuclear translocation of the transcription factor NF-κB (1). It was also found to significantly raise low glutathione (GSH) levels, thereby limiting lipid peroxidation (14).
Antiproliferative effects on human colon and lung cancer cells are due to growth-inhibition and apoptotic induction (15). In vitro and animal models suggest salicin can inhibit reactive oxygen species (ROS) and extracellular signal-regulated kinase (ERK) signaling pathways to produce antiangiogenic effects (4).
Due to potential for bleeding complications (16), willow bark should be discontinued before surgery or chemotherapy.
Those with impaired thrombocyte function should avoid willow bark, as it may interfere with blood clotting (2).
Allergy or sensitivity to salicylates such as aspirin.
Gastrointestinal discomfort; allergic reaction, erythema, pruritus (sudden rash, itching) (5)(7)(17).
May inhibit platelet aggregation or cause bleeding complications (2)(16). Anaphylaxis: In a 25-year-old woman with a history of allergy to acetylsalicylic acid, from the use of a supplement promoted for weight-loss that contained willow bark (18). Acute respiratory distress syndrome: In a 61-year-old woman with history of hypertension and osteoarthritis after taking a willow bark supplement. Symptoms included sudden dyspnea and non-productive cough, and there was no history of drug or supplement allergy (19).
Warfarin or other anticoagulants: When used concurrently, willow bark may increase the risk of bleeding (20).