Educational information, not medical advice — ask your doctor or midwife.
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Shomakakkonto is a Kampo herb formula from Japan. Its other name is Cimicifuga and Pueraria Decoction. It is a Single drug (Kampo): the four-herb mix counts as one product, and you take the whole set as it comes.
Kampo prescribers use it early in a fever with a skin rash. The classic case is the first days of a measles-like rash, when the fever has come and the spots are just showing. It is also used for some red, itchy rashes.
Here is the verdict in one line. Traditional standing is long, but modern human trial data is close to none. Traditional use is not proof that a remedy works, and that holds for this one too.
One more thing to know up front. The mix contains licorice root, so it is not a risk-free herb tea. Licorice can raise blood pressure and drop potassium in the blood, which is why this page is marked with a caution tier.
Nobody has proven how it works. The Kampo idea is that the mix helps a rash come out to the skin and cools "heat" in the body, so the fever passes sooner.
Lab work gives a few hints. Kudzu root holds plant compounds that calm swelling signals in cell and animal tests. Peony root and licorice root do something similar in the lab.
Lab dishes and mice are not people. No study shows that this formula changes how a rash illness runs in humans. Read the idea above as theory, not fact.
Most people in Japan take it as a dry granule or fine powder, sold in single-dose packets. You stir the dose into warm water and drink it.
Tablets and capsules of the same extract are also sold. A few practitioners still boil the raw herbs into a tea, which is the old way.
Strength differs between brands. Check the licorice amount on the pack, since that sets much of the risk.
The recipe comes from Chinese medical texts written about a thousand years ago, in the Song era. It was aimed at children with fever and early rash.
Japanese doctors took it up and reshaped it during the Edo period, and it became part of the Kampo set of standard formulas. It stayed in use in Japan as a listed Kampo product.
So the paper trail is old and steady. That is a fact about custom, not about proven effect.
See a doctor the same day if a fever with rash keeps climbing, if the rash spreads fast, blisters or turns purple, or if you feel very unwell.
Go straight to emergency care for trouble breathing, a stiff neck with headache, confusion, or a rash that does not fade when you press it.
Stop the formula and call a doctor if your ankles or face swell, your blood pressure climbs, your muscles feel weak or crampy, or your heartbeat feels odd. Also stop and get checked for yellow skin or eyes, dark urine, deep tiredness, or a new dry cough with breathlessness.
If the fever or rash is no better after two or three days, get it looked at rather than carrying on.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
The published evidence for Shomakakkonto is weak or absent. That usually means no controlled trial has tested it, not that a trial found it ineffective — the two are different, and we grade only what has been published.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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