Willow bark
Summary
Willow bark supplies salicin, which the body converts to salicylates. In a 210-person low back pain trial, 240 mg salicin a day left more people pain-free than placebo (grade D). Osteoarthritis results were mixed: a small 2-week trial helped, a larger 6-week trial did not. People allergic to aspirin should avoid it.
Key facts
- Bark extract standardized to salicin, a precursor of salicylic acid[1]
- Low back pain flare-ups (D); osteoarthritis pain (mixed, D); rheumatoid arthritis pain (no effect, D)[1][2][3]
- Pain-free in the final week: 39% on 240 mg salicin, 21% on 120 mg, 6% on placebo[1]
- In a 127-person trial, willow bark did not beat placebo, while diclofenac did[2]
- 3 graded human outcomes on this page
- October 11, 2026
How it works
ProposedSalicin is converted in the body to salicylic acid, a relative of aspirin; this is the proposed route to pain relief.[1]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Low back pain flare-ups | Improved | Grade D | RCT · n = 191 · 2000 Adults with an exacerbation of chronic low back pain (210 enrolled) Form: Willow bark extract · Dose: 120 or 240 mg salicin/day · Duration: 4 weeks Pain-free without rescue tramadol in the final week: 39% (high dose), 21% (low dose), 6% (placebo); one person had a severe allergic reaction, possibly to the extract. | 10936472 (opens PubMed)Source [1] |
| Hip or knee osteoarthritis pain | No effect | Grade D | RCT · n = 127 · 2004 Outpatients with hip or knee osteoarthritis Form: Willow bark extract · Dose: 240 mg salicin/day · Duration: 6 weeks Pain fell 17% with willow bark, 47% with diclofenac and 10% with placebo; willow bark did not differ significantly from placebo. A 26-person rheumatoid arthritis trial was also negative. | 15517622 (opens PubMed)Source [2] |
| Osteoarthritis pain | Improved | Grade D | RCT · n = 78 · 2001 Adults with osteoarthritis Form: Willow bark extract · Dose: 240 mg salicin/day · Duration: 2 weeks WOMAC pain fell 14% versus a 2% rise with placebo, a small but significant difference (6.5 mm). | 11406860 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Willow bark extract standardized to salicin | Varies[1][2][3] | No head-to-head human absorption data between products in our sources.[1][2][3] | One severe allergic reaction was reported in the back pain trial; otherwise tolerated.[1][2][3] | Low back pain and osteoarthritis (120–240 mg salicin/day) |
Studied doses
Doses studied in human trials ranged from 120 to 240 mg of salicin a day, from willow bark extract, for 2 to 6 weeks.[1][2][3]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Aspirin or salicylate allergy
- Willow bark delivers salicylates; one trial participant had a severe allergic reaction.[1]
- People on blood thinners or NSAIDs
- Salicin is converted to a salicylate, the same family as aspirin; the trials we cite did not study these combinations, so ask a clinician first.[1]
- Pregnancy and breastfeeding
- No safety data were found in the trials we cite.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Where to buy Willow bark
Products from brands we partner with that contain Willow bark. Listing a product is not a claim that it works; check the amount per serving against the doses studied above, and the label for other ingredients.
- SupersmartPaid linkWillow Bark Extract2 capsules: 80 mg salicin from 532 mg willow bark extract (15% salicin); 30 servings; this is below the 120–240 mg salicin/day used in the trialsShop at Supersmart (opens in new tab)Price and label checked 2026-10-11 on the brand’s site.
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Frequently asked questions
Does willow bark work for back pain?
In a 4-week trial, 240 mg salicin a day left 39% of people pain-free versus 6% on placebo.[1]
Does willow bark help arthritis?
Results are mixed: a 2-week trial found a small benefit, but a 6-week trial found no difference from placebo.[2][3]
Is willow bark the same as aspirin?
No, but its salicin is converted to a salicylate, so people allergic to aspirin should avoid it.[1]
Sources
- [1]Treatment of low back pain exacerbations with willow bark extract: a randomized double-blind study.. Am J Med, 2000. RCT
- [2]Efficacy and safety of willow bark extract in the treatment of osteoarthritis and rheumatoid arthritis: results of 2 randomized double-blind controlled trials.. J Rheumatol, 2004. RCT
- [3]Efficacy and tolerability of a standardized willow bark extract in patients with osteoarthritis: randomized placebo-controlled, double blind clinical trial.. Phytother Res, 2001. RCT
What changed
- First draft. Every PMID checked against NCBI E-utilities (title, year and journal taken from the PubMed record) and abstracts read for each cited row. Product details in Where to buy read from the brand page on the date shown. Self-reviewed in a second strict pass (no independent reviewer yet).