First, it may be helpful to know the many names of Dang Gui (pronounced Dong Gway), so we all know what herb we're talking about.

As you can see, Dang Gui, Dong Kwai and Angelica Root are the same thing. I will refer to them as Angelica.

Angelica has achieved notoriety as a women's herb. It has even been called the "Woman's ginseng." This is a misleading characterization, however, as the two herbs have completely different functions. Although it does not boost the qi like Ginseng does, Angelica does have actions specifically important to women:

Angelica tonifies the blood and regulates menstruation. If you are blood deficient, this is a very good herb (Blood deficiency is a general Chinese Medicine diagnosis which can include, but is not always, anemia.  Blood deficiency often manifests as pale skin, dryness, anxiety, insomnia, constipation, and poor memory). It is one of the most important herbs to deal with blood deficiency. It is commonly used for menstrual disorders resulting from a blood deficiency. This could manifest as irregular menstruation, not menstruating at all, or painful or difficult menstruation.

Angelica invigorates the blood and expels cold. There may be pain due to stagnant blood, which may manifest as abdominal pain, or carbuncles (boils with multiple drainage channels). Blood stasis may be caused by trauma, or cold from deficiency. Because Dang Gui is warming, however, people with heat conditions should avoid it unless it is part of a formula balanced for their condition.

Angelica moistens the intestines and unblocks the bowels. One uncomfortable result of blood deficiency is constipation. Angelica is not appropriate for all types of constipation, however. In Oriental Medicine there are many treatments for what seem to be the same symptoms, because we design our treatments based on the cause (the "root," not the "branch").For example, Western Medicine recognizes 'Asthma,' while Oriental medicine recognizes at least four types of Asthma, each requiring a different treatment.

Angelica reduces swelling, expels pus, generates flesh, and alleviates pain. By tonifying and invigorating the blood, Angelica can treat sores and abscesses (pus filled sores surrounded by dead or inflamed tissue).

Who should not take Angelica?

• Anyone with diarrhea and/or abdominal bloating - Angelica, like most blood tonics, is very substantial so it is hard on the digestion. It may cause indigestion and for this reason it is usually combined in formulas with herbs to strengthen the Stomach.
• People with yin deficient heat (mouth dryness, emaciation, irritability/anger, restlessness, feelings of heat, sweating at night, flush only on cheeks, sensation of fever in the afternoon); if you have some or all of these symptoms, Angelica will hurt more than help.

The good stuff
High quality Angelica is big, long, moist, oily, and aromatic. Avoid dry, and/or greenish/brown samples.

Research
Angelica appears to regulate contractions of the uterus, but does not appear to have any estrogenic effect. It may protect the liver. It lowers blood pressure, reduces heart plaque formation, inhibits bacteria (antibiotic), sedates the central nervous system, and alleviates certain types of pain.