Poultices, herbal preparations on hot towels placed over the skin, are another way to get herbs into one's body and to target specific tissues. Studies have shown better absorption of herbs and medications through the skin that when taken orally, and often with fewer side effects. How to use a poultice? According to Jethro Kloss in Back to Eden:

Do not warm over a poultice once used. Do not allow a poultice to become cold. Have a second poultice ready immediately upon removing the first one.
To make the following poultices it is best to have the herbs in a ground or granulated form. When using the herbs in powdered form, mix with just enough water to make a thick paste. When using them granulated, mix with water, cornmeal or flaxseed meal to make a thick paste. If fresh green leaves are used, beat them up, steep, and apply to the affected parts.
Poultices are most excellent for enlarged glands of any kind, such as neck, breast, groin, prostate, etc. Also for eruptions, boils, carbuncles, and abscesses. An excellent thing to do where any poultices are to be used is to bathe the affected part thoroughly with mugwort tea first. If you do not have this, cleanse it with hydrogen of peroxide before applying the poultice. It must be remembered that many herbs are used for poultices, so study the herbs and use those best suited to the condition, or those recommended for that condition.