White Willow Bark Extract Side Effects

White willow bark has been used for thousands of years as a treatment for fever and inflammation. It contains a chemical called salicin that is similar to the active ingredient in aspirin. Willow bark extract is available in capsule, liquid, or dried herb form. Most people can tolerate white willow bark, but some people have reported a number of side effects from its use.

Allergies and Side Effects

People who are allergic to aspirin should avoid white willow bark. The most common side effects of a willow bark intolerance or allergy include stomach upset, nausea and diarrhea. Some users have also experienced hoarseness, coughing and eye swelling. More serious symptoms such as dizziness, breathing difficulties, swelling, itching or rash may also occur. Medicine Net recommends consulting a doctor promptly if symptoms such as dizziness, confusion, black or tarry stool, a ringing sensation in the ears, or easy bruising develop. These symptoms can indicate a serious reaction to the herb. Willow bark can also cause a number of serious disorders. Renal papillary necrosis is a disorder characterized by tissue death in the kidneys. Its symptoms include bloody, cloudy or dark urine, back pain, incontinence and tissue inside the urine. Willow bark also creates a condition called hypertriglyceridemia, or too many fat cells in the bloodstream. Hyperuricemia, which means that there is a high uric acid level in the blood, is another harmful side effect.

Drug and Alcohol Interactions

Acetazolamide is a medication used to treat seizure disorders and glaucoma, and is also sometimes prescribed as a remedy for altitude sickness. A combination of white willow bark and acetazolamide results in confusion, a lack of energy and bladder control problems. Some drugs increase the risk of bleeding in patients; white willow bark can worsen these effects. Do not use white willow bark with medications such as warfarin or heparin, which are anticoagulants that prevent blood clots in the lungs, arteries and heart, or with aspirins or other aspirin-like medications. Willow bark increases the levels of methotrexate, which is a drug used to slow the growth of cells, and the anti-seizure medication phenytoin, to toxic amounts. Do not use willow bark in combination with either of these medications. Willow bark also decreases the effectiveness of diuretics and beta-blockers. It causes stomach inflammation and bleeding inside the gastrointestinal tract when used in combination with alcohol.

Mothers and Children

Pregnant women are advised to avoid willow bark because salicylates, or aspirin chemicals, are dangerous to unborn babies. They can also cause rashes in breastfed babies whose mothers use salicylates. Children from the ages of 4 to 12 who use aspirin are at risk of developing a serious infection called Reye's Syndrome that causes liver dysfunction and sudden brain damage. Reye's syndrome usually follows the onset of chicken pox or respiratory infections by about a week,so it should not be given to children who are suffering from chicken pox or any other viral infections. The University of Maryland recommends not giving white willow bark to children under the age of 16.