What folk medicine says: Called plague-flower for its use as a bubonic plague remedy, butterbur was also “good for those that wheeze much,” said the early 17th-century herbalist Culpeper. What new research confirms: In a study conducted in four Swiss and German general medicine and allergy clinics, 125 hay fever sufferers were split into two groups. One received butterbur root extract; the other, cetirizine (Zyrtec), a prescription antihistamine. After 2 weeks of treatment, the butterbur and cetirizine were equally effective at easing the general discomfort and lack of energy often associated with spring allergies, says study author Andreas Schapowal, MD, a Swiss ear, nose, and throat surgeon. In subsequent research, Schapowal found that treatment with butterbur extract (this time for 5 days) also reduced nasal allergy symptoms, including sneezing, itching, runny nose, stuffiness, and watery eyes. Why it might work: Butterbur contains compounds called petasines. These blunt the activity of leukotrienes, substances in the body that can trigger allergic responses. What to buy: A good source of butterbur is Petadolex, a standardized extract available at health food stores. Dose: One softgel, three times a day. Price: $49.95 for 60 softgels. More from Prevention: How Yoga Helps Allergies