White Willow Bark: Salicin, Aspirin, Research and Safety

White willow bark is the bark of the Salix alba tree, and it contains salicin, a natural compound the body turns into salicylic acid, a relative of aspirin. Willow bark extract is sold as an herbal supplement and appears in some topical products. Small trials suggest it may ease low back pain in the short term, while osteoarthritis results are mixed. Because it is a salicylate, it carries many of the same cautions as aspirin, including Reye’s syndrome in children and bleeding risk with blood thinners. Here is what the research shows and who should avoid it.

This article is general information, not medical advice. Back pain that is severe, follows an injury, or comes with numbness, weakness, fever or bladder changes needs a clinician, not a supplement.

What is white willow bark?

Willow trees have been used for pain and fever for more than 3,500 years, according to a history of aspirin published in the British Journal of Haematology. That story runs from an Oxfordshire clergyman who wrote about willow bark to scientists at a German dye company who developed aspirin, now the most commonly used drug in the world. Memorial Sloan Kettering Cancer Center (MSK) lists salicin as the main active compound in Salix alba bark, along with catechol and flavonoid compounds.

In Europe, willow bark is also regulated as an herbal medicine. The European Medicines Agency’s 2017 monograph recognizes a dry extract as having well-established use for the short-term relief of low back pain, and lists traditional uses for minor joint pain, fever with a common cold and headache. In the US, willow bark extract is sold as a dietary supplement, which the FDA does not approve before sale.

White willow bark vs aspirin

Salicin is sometimes called “natural aspirin,” but the two are not interchangeable. A pharmacology study in volunteers found salicylic acid was the main salicin breakdown product in the blood, but blood salicylate levels were much lower than after pain-relief amounts of aspirin. The authors concluded salicylic acid alone probably does not explain willow bark’s effects, and a later study detected catechol compounds in the blood as well.

That platelet difference comes from a small trial of 51 people: willow bark extract affected platelet clumping far less than heart-protective aspirin. MSK states plainly that willow bark should not be used as a substitute for aspirin because its potency varies. Anyone told to take aspirin for heart protection should not swap it for willow bark.

White willow bark benefits: what the research shows

Most willow bark research involves pain, and the studies are small. These are research summaries, not a reason to skip a medical evaluation.

Low back pain

A 2014 Cochrane review of herbal medicines for low back pain concluded that white willow bark extracts are probably better than placebo for short-term pain and for reducing the need for rescue pain medicine, based on two trials with 261 participants and moderate-quality evidence. The largest of those trials, published in 2000, followed 210 people with flare-ups of chronic low back pain for four weeks; 39% of the higher-strength group were pain-free in the final week, compared with 6% on placebo. One person had a severe allergic reaction that may have been caused by the extract. The Cochrane review noted poor reporting across trials, and its senior author had previously worked for a company selling ingredients it reviewed. Topical capsicum had the strongest evidence in that review; see our cayenne pepper guide.

Osteoarthritis and rheumatoid arthritis

A 2004 pair of German trials found willow bark extract was not significantly better than placebo for hip or knee osteoarthritis pain over six weeks, while the drug diclofenac was. A smaller rheumatoid arthritis trial also found no significant difference. A 2009 systematic review called the osteoarthritis results conflicting, and a 2019 evidence panel for military personnel recommended against willow bark extract for chronic musculoskeletal pain. Joint conditions need a clinician’s diagnosis and plan.

Weight loss

MSK lists weight loss among willow bark’s purported uses but describes no evidence for it. If a weight-loss product lists willow bark, consider it an unproven extra. Our ginger guide covers another plant often marketed for comfort and digestion with similar evidence limits.

White willow bark side effects and who should avoid it

The EMA monograph lists allergic reactions such as rash, itching, hives and asthma, and digestive effects such as nausea, vomiting, stomach pain, diarrhea, indigestion and heartburn. MSK also notes rare case reports of severe allergic reactions and breathing problems. The EMA says willow bark should not be used by people with:

• Allergy or sensitivity to salicylates, aspirin or other NSAIDs, including asthma triggered by salicylates.
• Active stomach ulcers.
• Age under 18, because of the risk of Reye’s syndrome. MedlinePlus advises against giving aspirin or products with aspirin-like salicylates to a child with a cold or fever.
• Third-trimester pregnancy; the EMA also does not recommend it earlier in pregnancy or while breastfeeding, because salicylates cross the placenta and appear in breast milk.
• G6PD deficiency, severe liver or kidney disease, or a bleeding or clotting disorder.

Drug interactions: the EMA says willow bark may increase the effects of anticoagulants such as warfarin, and advises against combining it with other salicylates or NSAIDs such as aspirin, ibuprofen or naproxen without medical advice. MSK adds that it should be stopped before surgery. Tell your clinician and pharmacist about willow bark, as you would any medicine. For back or joint pain, the EMA advises against use beyond four weeks without medical advice.

Willow bark extract in topical products

Willow bark extract also shows up in creams and lotions. Two CBD topicals in our catalog list it: CBDfx CBD Cream for Muscle & Joint, Cooling Formula, which pairs broad spectrum hemp extract with menthol, caffeine and white willow bark extract, and CBDfx CBG + CBD Lotion, Heating Formula, which adds camphor. Both are cosmetic topicals for external use only, and both labels say to ask a doctor before use if you are sensitive to salicylates, pregnant or nursing. The trials above tested oral extracts, not these products, so no effect is claimed. Our guide to CBD cream vs oil explains how topicals differ, and CBD drug interactions covers medicine questions.

How to check a willow bark label

• Look for the plant name (Salix alba or another Salix species) and the part used (bark).
• Check whether the extract is standardized to salicin; unstandardized products can vary widely.
• Note other pain-related ingredients that could stack salicylates or caffeine.
• Look for an independent quality seal; our third-party testing guide explains what seals mean.
• Read the warnings section for salicylate allergy, pregnancy and blood thinner statements.

If you are reading about cartilage supplements in the same aisle, our chondroitin guide explains that evidence.

Frequently Asked Questions

Questions about a label? Contact us or read our Buyer’s Guide. Follow the label and ask a healthcare provider before starting any supplement, especially if you take medicines. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

Last reviewed October 2026.

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