White willow bark was used as early as 400 B.C., according to the University of Maryland Medical Center. Patients chewed on willow bark to relieve pain and inflammation. White willow (salix alba) is also known as European willow. Commercial willow bark is sold in capsule form in natural food stores as an alternative/herbal medicine. People who are allergic to aspirin should avoid taking willow bark. Some people experience stomach upset when taking willow bark. Consult your physician before taking this or any other medication.
Willow bark contains salicin, from which salicylic acid, the active ingredient in aspirin, was first derived. According to the University of Maryland Medical Center, white willow is not as fast-acting as aspirin, but its effects may last longer.
The salicin in willow bark acts to reduce inflammation, but researchers at UMMC theorize that other anti-oxidant and antiseptic properties of white willow bark may combine with salicin to enhance the bark's anti-inflammatory properties.
A study conducted by researchers from the Rambam Medical Center in Haifa, Israel in 2000 concluded that 240 mg doses of willow bark extract administered to study participants daily for four weeks resulted in decreased back pain for 39 percent of patients.
Researchers at Tubingen University in Germany found in a 2000 study of patients with osteoarthritis experienced relief from pain and stiffness with daily doses of 240 mg of willow bark extract over a four-week period.