Due to the presence of volatile oil constituents in hyssop, it may provide relief for mild irritations of the upper respiratory tract that accompany the common cold. The expectorant action of hyssop’s volatile oil may partially explain its traditional use for coughs, asthma, and bronchitis.⁴ The volatile oils are also thought to contribute to hyssop’s carminative actions and use for mild cramping and discomfort in the digestive tract. The German Commission E has not approved hyssop for any medical indication.⁵ Test tube studies have found that certain fractions of hyssop (one being a polysaccharide designated as MAR-10) may inhibit the activity of the human immunodeficiency virus (HIV).^{6, 7} Yet, there have been no studies in humans to determine whether hyssop or any of its constituents are effective in treating HIV infection or AIDS.