Educational information, not medical advice — ask your doctor or midwife.
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Can Sha is the dried droppings of the silkworm, also known as Silkworm Feces. It is a single drug (TCM herb), not a blend or a formula. Herbalists use it mainly for achy, stiff joints and for an upset stomach with vomiting, cramps and loose stools.
Silkworms eat only mulberry leaves, so the droppings are mostly part-digested leaf. The grains are dried, sieved clean, and simmered into a tea. Because the bits float and cloud the water, they are nearly always cooked inside a small cloth bag.
Here is the plain verdict. Can Sha has a long, steady record in Chinese medicine, but we could not find any human trial of it. A long history of use is not proof that something works, and we say that once here rather than at the top of every section below.
No one has shown how Can Sha works in the body, and the honest answer is that we do not know.
In Chinese medicine terms, Can Sha is said to drive out "wind-damp" from the joints and to settle a churning stomach. That is a traditional way of sorting symptoms, not a description of body chemistry.
Lab work points to the green leaf pigment and other plant leftovers in the droppings. Some of these have calmed swelling in test tubes and in animals. That is a long way from showing an effect in a person.
Can Sha comes in a few forms. The usual one is loose dried grains, simmered in a cloth bag to make a tea.
- Powder, sometimes packed into capsules. - An ingredient inside ready-made Chinese formulas. - A wash or soak for itchy skin, used on the skin only.
Buy only from a supplier that cleans, dries and tests the material. Never collect or use it yourself from a farm or a hobby setup.
Can Sha has been used in China for many hundreds of years and is listed in the classic herb books, including the Ben Cao Gang Mu of 1596.
Its best-known use is in Can Shi Tang, a formula written down by Wang Meng-ying in the 1800s for violent vomiting, diarrhoea and leg cramps.
It is a long-standing staple of one tradition, Chinese medicine. It has no matching record in Western, Ayurvedic or other herb systems.
Get emergency help if your face, lips or tongue swell, if hives spread over your body, or if you struggle to breathe. These are signs of a serious allergy.
See a doctor the same day if vomiting or diarrhoea will not stop, if you cannot keep fluids down, if you pass very little urine, or if you feel dizzy when you stand. These are signs you are drying out.
Book a normal appointment if a joint is hot, red or swollen, if joint pain lasts more than two weeks, or if bloating keeps coming back. Tell your doctor and your pharmacist that you are taking Can Sha.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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