What could be nicer on a cold day when you don’t feel so hot than a cup of tea? Make your own infusions, which are water-based herb extracts, by simply pouring water over a medicinal and allowing it to sit for a while. (Do this when plants are delicate or aromatic for maximum effects.)
According to Western Herbs According to Traditional Chinese Medicine: A Practitioner’s Guide, by Thomas Avery Garran, hot infusions are used for lighter plant material, such as flower and leaf that is delicate and may contain essential oils that would evaporate in a decoction. To make a hot infusion, pour boiling water over a single herb or mixture of herbs in a cup, or teapot, or tea strainer. Allow the vessel to stand, covered, for 3 to 30 minutes. The length of time is primarily determined by the plant, which has a lot to do with what you are trying to extract. Flower petals require a very short infusion time, while aromatic roots, such as aucklandia, will require a much longer steeping.
Cold infusions are used less frequently, but when applied properly, can be of equal therapeutic value. Cold infusions are useful for processing herbs containing constituents that may be sensitive to heat. For example, heat destroys the cyanogenic glycosides in wild cherry bark, so the bark is infused overnight in cold water. Herbs with a high starch or mucilage content are also better extracted with cold water.
Try this classic diaphoretic infusion, from Western Herbs According to Traditional Chinese Medicine.
1 part elder flowers
1 part peppermint
1 part yarrow
20 parts boiling water
Place the herb in a pot, pour boiling water over it and allow to stand for 30 minutes. This infusion should be drunk warm by the cupful as frequently as desired. Instruct the patient to bundle up to encourage diaphoresis. This formula, a good example of a classic infusion, is useful for colds and influenza with symptoms such as sore throat and fever with little or no sweating. For chills, add 1 to 3 parts fresh ginger to the above formula.