Eyebright is an annual herb common in grassy areas throughout much of Europe, western Asia, and the subarctic regions of North America. Reaching up to 20 centimeters in height, eyebright has stiff, ovate leaves, which are roughly 13 mm long and 8 mm wide, positioned opposite at the base of the plant and alternate toward the top. The plant is hemiparasitic; the roots have nodules that attach to the roots of other plants to obtain nutrients. Eyebright flowers from June to September, producing white or pale purple, two-lipped blossoms, which are often marked with purple and yellow spots and stripes. The fruit of the plant consists of small, flattened capsules, which contain numerous ribbed seeds.
Chemical studies of eyebright have identified several constituents, including aucubin, caffeic acid, ferulic acid, sterols, choline, and a volitile oil. However, no therapeutic activity for any of these compounds has been demonstrated in scientific studies.
For an eyewash or tea, a common recommendation is 28 grams of the herb steeped in 500 ml of boiling water. The dried herb is also available in capsules, for which the usual dosage ranges from 800 to 1400 mg per day. While the tea can be consumed liberally with no adverse effects, out of concern for harmful impurities, Germany's Commission E (the German government's expert panel on herbal remedies) does not recommend external application of eyebright infusions to the eyes.