Getting away from colds and sinus infections for a moment, I think the following paper is interesting. This paper presents a study of orally taken oregano in hyperlipidemic human patients. (Hyperlipidaemia just means that these people have elevated levels of fat in their blood, for example too much cholesterol.)
After regularly taking oregano oil supplements following each meal for 3 months, these patients had improved lipid profiles including higher HDL (good cholesterol), lower LDL (bad cholesterol), improved antioxidant status (which, theoretically, could help fight cancer and reduce heart disease), and improved endothelial function (healthier veins and arteries) compared to those who did not take the oregano supplement.
Effects of Origanum onites on endothelial function and serum biochemical markers in hyperlipidaemic patients.
Ozdemir B, Ekbul A, Topal NB, Sarandöl E, Sağ S, Başer KH, Cordan J, Güllülü S, Tuncel E, Baran I, Aydinlar A.
J Int Med Res., 2008 Nov-Dec, 36(6), 1326-1334.