Is Willow Bark Nature’s Aspirin?

Willow bark contains compounds similar to those in aspirin and has a long history of use for easing pain. It is sold as a supplement in multiple preparations, though these products are not regulated. Scientific findings about its benefits are mixed.

Derived from the bark of several willow species, willow bark has been employed for centuries to address inflammation and pain.

Some people opt for willow bark as an alternative to aspirin, especially those coping with persistent headaches or lower back pain. It also appears as an ingredient in some products marketed for weight management.

Below we cover what willow bark is, how it may act like aspirin, and what current research indicates.

What is willow bark?

Willow bark is harvested from the branches of willow trees that are about two to three years old. Willow trees and shrubs are found across the globe, with the exception of Australia and Antarctica.

Common willow species used include:

• Salix purpurea (purple willow)
• Salix fragilis (crack willow)
• Salix alba (white willow)
• Salix daphnoides (violet willow)
• Salix pentandra (bay willow)

White willow and black willow are among the most frequently used medicinal varieties.

Potential benefits

Besides various polyphenols, willow bark contains salicin. Salicin is an alcohol-type molecule that includes a β-glucoside component. After ingestion, the body splits it into glucose and salicyl alcohol. Salicyl alcohol is then oxidized to form salicylic acid.

Salicylic acid may help  reduce the production of prostaglandins, substances that promote inflammation and pain.

Salicylic acid is the simplest member of a family of compounds called salicylates. This explains why willow bark might share similarities with aspirin , which is rapidly metabolized into salicylic acid in the body.

Historically , Native American groups chewed willow bark to alleviate pain. Today, people may use it for issues such as back pain, osteoarthritis, or muscle soreness. It’s commonly included in a variety of supplement formulas.

However, robust scientific proof supporting its effectiveness for these conditions remains limited.

Here’s a summary of research findings:

Arthritis

A 2023 review  of 329 patients with various forms of arthritis reported that those taking willow bark experienced greater symptom relief compared with placebo.

Older studies assessing willow bark extract in osteoarthritis (OA) and rheumatoid arthritis (RA) produced inconsistent outcomes.

Some trials showed no measurable difference from placebo or standard drugs, while others observed small improvements that were not statistically significant.

Since many arthritis types involve inflammation, studies focusing on musculoskeletal pain such as OA or nonspecific back pain tended to report modest pain reduction with generally mild side effects.

Variations in results may reflect differences in the preparation, willow species used, or dosing protocols.

Antimicrobial properties

A 2021 study  indicates two willow bark extracts might exert notable anti-inflammatory effects on peptides and inflammatory cells associated with COVID-19.

More investigation is necessary to determine whether willow bark can truly reduce viral-driven inflammation, such as fever.

Another 2021 paper  evaluated 16 northern willow species using a mild hot water extraction and explored their potential for natural-product uses.

That work found all tested types may show antiviral activity against viruses like coxsackievirus A9 and antibacterial effects against organisms such as Staphylococcus aureus and Escherichia coli (E. coli), though they were less active against fungi.

Effects varied by species, and further studies are needed to confirm these results in humans.

Skin aging

A 2024 in vitro study examined specific polyphenols from Salix chaenomeloides on human skin cells.

Findings point to possible benefits for reducing photoaging and inflammation while enhancing antioxidant defenses, but clinical trials in people are required to validate these laboratory observations.

Weight loss

Willow bark is frequently added to dietary supplements — products that are not reviewed by the FDA.

There is very limited evidence  supporting its use for weight reduction. Additional research is needed to clarify whether any willow species affects body weight in humans.

Side effects and risks

In moderate amounts, willow bark generally seems well tolerated. Excessive use, however, can lead to stomach cramps and bleeding.

Less common adverse effects may include:

• breathing difficulties
• hemolytic anemia
• liver failure

Because some willow species can absorb heavy metals from soil, there is a risk of heavy metal exposure from contaminated bark extracts.

Allergic reactions to willow bark can occur and may be life-threatening in some cases. People with known aspirin sensitivity are at higher risk.

Anaphylaxis

Anaphylaxis is a rapid, severe allergic response that can be fatal.

Signs may appear suddenly and include:

• dizziness or lightheadedness
• trouble breathing or wheezing
• fast heartbeat
• confusion
• anxiety
• clammy skin
• fainting or loss of consciousness
• hives
• swelling
• abdominal pain, nausea, or vomiting

If anyone develops these symptoms, you should:

1. Check whether they carry an epinephrine auto-injector and, if present, follow the instructions to administer it.
2. Call 911 or your local emergency number.
3. Lay the person down; if they have vomited, position them on their side.
4. Remain with them until emergency responders arrive.

More than one epinephrine dose may be needed; if symptoms persist after 5 minutes and another injector is available, administer a second dose.

Willow bark can interact with medications such as anticoagulants, beta-blockers, and even acetaminophen (Tylenol) — with at least one reported association with Reye’s syndrome.

Children and teens under 16 are at higher risk for Reye’s syndrome and should avoid willow bark.

Pregnant and breastfeeding people are advised against taking salicylate-containing products.

Individuals with gastric ulcers should use caution, similar to caution taken with aspirin, since excessive use could cause gastrointestinal bleeding.

Forms and dose of willow bark

Willow bark is sold as a supplement in several formats, including capsules available at many pharmacies and health food outlets.

Research-based dosing for pain relief typically cites about 240 milligrams (mg) per day.

It may also be applied topically in creams or included in skincare products. Other delivery methods are:

• chewing the raw bark
• using a tincture
• brewing it as a tea

When consumed in these traditional forms, it is difficult to know the exact amount of active compounds per dose.

Because willow bark can potentially accumulate heavy metals and supplement quality varies, exercise caution when choosing any extract.

Takeaway

Willow bark appears to offer relief for some mild pain conditions, but more rigorous research is required to determine how it compares to aspirin and whether it is reliably effective for various ailments in people.

It may be a useful alternative to aspirin for certain individuals, but consult a healthcare professional before using willow bark.