The bark of white willow contains salicin. In combination with the herb’s powerful plant compounds (called flavonoids), salicin is thought to be responsible for the soothing effects of the herb.

In contrast to aspirin, willow bark doesn’t damage the gastrointestinal mucosa and doesn’t affect blood thinning to the same degree as aspirin. Unlike aspirin, white willow bark contains plant chemicals called polyphenols and flavonoids that have antioxidant, fever-reducing, and immune-boosting properties. Studies indicate the effects of white willow take longer than aspirin to kick in, but they tend to last longer and to cause fewer adverse reactions.