Yarrow: Ancient Insect Repellent - First Ways: "If you plan on spending time outdoors this summer, then yarrow, Achillea millefolium, is a very useful herb to know about. As the title of this post suggests, you can make an alcohol extract of the upper parts of the yarrow plant — the leaves and flowers — and spray it as an insect repellent. (The recipe is one part herb per two parts liquid menstruum, which should be 50% alcohol).
Yarrow has other applications, too. If you’re out hiking and you cut yourself, applying the fresh leaves and flowers topically will stop bleeding and disinfect the area. If you pick the plant now, you can dry and powder it to have on hand for first aid later. And you can also brew a warming tea with the dried yarrow as a cold remedy. Herbalists say it’s good for sweating out a fever. If you make the tincture described above as an external insect repellent, you also could use it internally as an antibiotic to treat dysentery or urinary tract infections, according to herbalist Stephen Buhner..."