- Bay willow
- Black willow
- White willow
For Patients & Caregivers
How It Works
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. A case of allergic reaction was reported following use of a weight-loss product that contained willow bark.
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
- Salicin affects platelet aggregation, although to a lesser extent compared to acetylsalicylate. The clinical significance of this effect in patients with impaired thrombocyte function is yet to be determined.
- 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.
- Fatal Fulminant liver failure in a 28-month-old boy after being treated for upper respiratory infection with acetaminophen and a tea containing willow bark.
For Healthcare Professionals
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. Aspirin is derived from salicin, an active compound in willow bark.
Willow bark extracts demonstrated anti-inflammatory (1), antiproliferative (3) and skin-protective (23) effects in vitro. Clinical studies indicate that willow bark may help manage back pain (5) (6) (24), although studies of osteoarthritis are mixed (7) (8) (9), with negative findings for rheumatoid arthritis (6) (9). Topical application of salicin may help reduce skin aging (10).
Preclinical studies have shown that salicin has antiangiogenic (4) , anticancer (25) and chemopreventive effects (26). It was also found to modulate neurite growth in human neuroblastoma cells (27). Aspirin 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), the 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 in human colon and lung cancer cells are due to growth-inhibition and apoptotic induction (15). In vitro and animal models suggest that salicin can inhibit reactive oxygen species (ROS) and extracellular signal-regulated kinase (ERK) signaling pathways to produce antiangiogenic effects (4).
Gastrointestinal discomfort; allergic reaction, erythema, pruritus (sudden rash, itching) (5) (7) (17)
Salicin affects platelet aggregation, although to a lesser extent compared to acetylsalicylate (2). The clinical significance of this effect in patients with impaired thrombocyte function is yet to be determined.
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).
Fatal Fulminant liver failure: In a 28-month-old boy after being treated for upper respiratory infection with acetaminophen and a tea containing willow bark (28).