Willow bark comes from several varieties of willow tree, including white (Salix alba or European), black (Salix nigra or pussy), crack, and purple willow.
Willow bark contains a chemical called salicin, which is similar to aspirin. It has pain and fever reducing effects in the body.
People commonly use willow bark for back pain, osteoarthritis, fever, flu, muscle pain, and many other conditions, but there is no good scientific evidence to support most of these uses. There is also no good evidence to support using willow bark for COVID-19.
Is It Effective?
NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
- Back pain. Taking willow bark by mouth seems to reduce lower back pain. Higher doses seem to be more effective than lower doses, and it may take up to a week to help.
There is interest in using willow bark for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.
Is it Safe?
When taken by mouth: Willow bark is possibly safe when used for up to 12 weeks. It might cause diarrhea, heartburn, and vomiting in some people. It can also cause itching, rash, and allergic reactions, particularly in people who are allergic to aspirin.
Special Precautions & Warnings:
Pregnancy: There isn't enough reliable information to know if willow bark is safe to use when pregnant. Stay on the safe side and avoid use.
Breast-feeding: It is possibly unsafe to use willow bark while breast-feeding. Willow bark contains chemicals that can enter breast milk and have harmful effects on the nursing infant. Don't use it if you are breast-feeding.
Children: Willow bark is possibly unsafe when taken by mouth for viral infections such as colds and flu. There is some concern that, like aspirin, it might increase the risk of developing Reye syndrome. Stay on the safe side and don't use willow bark in children.
Bleeding disorders: Willow bark might increase the risk of bleeding in people with bleeding disorders.
Kidney disease: Willow bark might reduce blood flow through the kidneys. This might lead to kidney failure in some people. If you have kidney disease, don't use willow bark.
Sensitivity to aspirin: People with asthma, stomach ulcers, diabetes, gout, hemophilia, hypoprothrombinemia, or kidney or liver disease might be sensitive to aspirin and also willow bark. Using willow bark might cause serious allergic reactions. Avoid use.
Surgery: Willow bark might slow blood clotting. It could cause extra bleeding during and after surgery. Stop using willow bark at least 2 weeks before a scheduled surgery.
Acetazolamide
Interaction Rating=Moderate Be cautious with this combination.
Willow bark contains chemicals that might increase the amount of acetazolamide in the blood. Taking willow bark along with acetazolamide might increase the effects and side effects of acetazolamide.
Aspirin
Interaction Rating=Moderate Be cautious with this combination.
Willow bark contains chemicals similar to aspirin. Taking willow bark along with aspirin might increase the effects and side effects of aspirin.
Choline Magnesium Trisalicylate (Trilisate)
Interaction Rating=Moderate Be cautious with this combination.
Willow bark contains chemicals that are similar to choline magnesium trisalicylate. Taking willow bark along with choline magnesium trisalicylate might increase the effects and side effects of choline magnesium trisalicylate.
Medications that slow blood clotting (Anticoagulant / Antiplatelet drugs)
Interaction Rating=Major Do not take this combination.
Willow bark might slow blood clotting. Taking willow bark along with medications that also slow blood clotting might increase the risk of bruising and bleeding.
Salsalate (Disalcid)
Interaction Rating=Moderate Be cautious with this combination.
Salsalate is a type of medicine called a salicylate. It's similar to aspirin. Willow bark also contains a salicylate similar to aspirin. Taking salsalate along with willow bark might increase the effects and side effects of salsalate.
Herbs and supplements that might slow blood clotting: Willow bark might slow blood clotting and increase the risk of bleeding. Taking it with other supplements with similar effects might increase the risk of bleeding in some people. Examples of supplements with this effect include garlic, ginger, ginkgo, nattokinase, and Panax ginseng.
Herbs that contain chemicals similar to aspirin (salicylates): Willow bark contains chemicals called salicylates. Salicylates are similar to aspirin. Taking it with other supplements that contain salicylates might increase their effects and side effects. Examples of supplements that contain salicylates include aspen, black haw, poplar, and meadowsweet.
There are no known interactions with foods.
Willow bark has most often been used by adults in doses providing 120-240 mg of salicin by mouth daily for up to 6 weeks. Speak with a healthcare provider to find out what dose might be best for a specific condition.
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