What is Xia Ku Cao?

Xia Ku Cao is a dried flower spike from the selfheal plant, Prunella vulgaris. It is a single herb, not a mixed formula. It is also called Prunella spike, or selfheal spike.

In Chinese medicine it is used for red, sore eyes and for headache with dizziness. It is also used for lumps in the neck, such as a swollen thyroid gland or swollen glands. Some people take it as a tea for high blood pressure.

Here is the short verdict. The herb has a long and solid place in Chinese medicine, but good human trials are lacking. Long use in a tradition is not proof that a herb works, so read the rest of this page with that in mind.

How does Xia Ku Cao work?

No one has shown how it works in the human body. In test tubes and in animals, extracts of the spike lower blood pressure a little and calm swelling. Lab and animal work is not proof of an effect in people.

In Chinese medicine, it is said to clear "liver fire" and to soften lumps. That is a way of sorting symptoms, not a body process anyone can measure.

Some of its plant acids kill germs and act as antioxidants in lab dishes. An antioxidant mops up unstable molecules that can damage cells. Whether any of this happens after you drink a cup of the tea is not known.

What forms does Xia Ku Cao come in?

The plain dried spike is the usual form. You simmer it in water to make a strong tea, called a decoction.

You can also find it as granules that dissolve in hot water, as capsules or tablets, and as a liquid tincture. In southern China it is a common part of cooling herbal tea drinks.

It also appears in ready-made Chinese products such as Xia Ku Cao Gao, a sweet syrup. Those products often hold several herbs, so check the label. This page is about the single herb only.

Where it comes from:

Xia Ku Cao has been used in China for about 2,000 years. It is listed in the Shen Nong Ben Cao Jing, one of the oldest Chinese herb books. Its name means "summer withering grass", because the plant dries out in midsummer.

It has stayed a standard herb in Chinese medicine ever since. Classic texts group it with herbs that cool the eyes and shrink neck lumps.

The same plant grows in Europe, where it was called selfheal and put on wounds. That use is different from the Chinese use of the dried spike.

What does Xia Ku Cao help with?

• Red, sore or gritty eyes: This is the classic Chinese use, often paired with chrysanthemum flower. Texts describe it for eyes that feel hot, sore and worse in the afternoon. There are no good human trials for this use. Eye pain with blurred sight needs a doctor, not a tea.
• Headache with dizziness: Chinese practice uses it for headache linked to what it calls rising liver fire. That means a hot, tense, irritable pattern with a pounding head. Human trial support is absent. It is a traditional use only.
• Swollen thyroid gland (goitre): Old texts use it for lumps and swellings in the neck, including goitre. Modern Chinese hospitals sometimes add it to thyroid formulas. The published trials are small, poorly controlled and hard to trust. A neck lump must be checked by a doctor first.
• Swollen lymph glands in the neck: Traditional texts describe it for hard, cord-like glands under the jaw. This was tied to old tuberculosis of the glands. There is no modern trial evidence, and swollen glands that last more than two weeks need medical review.
• High blood pressure: Animal work shows a mild drop in blood pressure, and the herb makes some people pass more urine. Human evidence is weak and the studies are small. It is not a replacement for blood pressure medicine, and mixing the two can drop your readings too low.
• Breast lumps and breast pain: It appears in Chinese formulas for tender, lumpy breasts and for mastitis, an infected breast. Evidence is traditional, not tested. Any new breast lump needs a doctor's check without delay.
• Mild skin swelling and boils: It is used, usually with other herbs, for hot red skin swellings. Lab work shows some germ-killing action. No human trials support this use.

Which foods are rich in Xia Ku Cao?

1. Chinese cooling herbal teas (liang cha): bottled and shop-made drinks in southern China often list Prunella spike
2. Herbal soup mixes: the dried spike is sometimes simmered with other herbs in home soups

Practical Tips:

It is a medicinal herb, not a food, so no ordinary diet supplies it.

What are the side effects of Xia Ku Cao?

• Upset stomach or nausea
• Loose stools or diarrhoea
• Passing more urine than usual
• Dizziness or feeling faint, more likely if your blood pressure drops
• Skin rash or itching from an allergy
• Mouth dryness

Good to know:

Side effects are not common and are usually mild. Stomach upset is the one people report most, and it often settles if you take it after food.

Allergy is rare but possible, more so if you react to mint-family plants. Stop the herb if you get a rash, swelling or wheezing.

How much Xia Ku Cao should you take?

• Recommended daily: No trial-tested dose exists. Chinese practice uses 9 to 15 grams of the dried spike a day, simmered in water. Some texts allow up to 30 grams a day, but that belongs under a trained practitioner. For tablets, capsules or granules, follow the label. Products vary in strength, so do not assume two brands match.
• Best time of day: Split the daily amount into two doses, morning and early evening. It may make you pass more urine, so avoid a dose right before bed.
• With or without food: Take it after food. The tea is bitter and can upset an empty stomach.
• Time to effect: Not known from trials. In traditional use, eye redness and headache are reviewed after about a week. Any change in blood pressure would take weeks and must be measured, not felt.
• How long to take it: Traditional use is short, usually two to four weeks at a time. Stop and get advice if nothing has changed after four weeks. If you take it for blood pressure, have your readings checked rather than guessing. Long daily use for months has not been studied for safety.