An ordinary Vietnamese habit
In Vietnamese households, rice is rinsed before it is cooked, and the cloudy water that comes off it — nước vo gạo — was kept rather than poured away. It went to the garden, to the animals, and to hair. Left covered for a few days it soured, and that soured water was used as a rinse, often after a bồ kết wash.
No ceremony was attached to it. It was the useful by-product of something that happened in every kitchen, every day. That is the whole provenance, and it is enough: what matters for a formulation is not how old a practice is, but what is measurably in the liquid.
“The tradition tells us where to look. It does not tell us what we are allowed to claim.”
The key molecule: inositol
When rice is soaked and allowed to ferment, the fermentation process breaks down larger molecules into smaller, more bioavailable forms. The result is a liquid rich in inositol — a carbohydrate with an unusual property in cosmetic science: it is small enough to penetrate the hair shaft rather than sitting on its surface.
Most conditioning agents work by coating the outside of the hair fibre, smoothing the cuticle layer and reducing friction. Inositol works differently. The available research — a small evidence base, not a large one — indicates that inositol remains inside the hair fibre after rinsing and improves its resistance to mechanical stress. We grade this supported, not well established.
Why fermentation is not optional
Plain rice water contains many of the same compounds as fermented rice water, but at lower concentrations and in less bioavailable forms. Fermentation lowers the pH of the liquid, which helps close the hair cuticle and enhances shine, while increasing inositol concentration — the molecule most directly linked to hair strength benefits.
5–10%: the functional concentration range
Published guidance for Oryza Sativa Ferment Filtrate sets a functional range of up to 10% for rinse-off products. Our shampoo and Rice Water Conditioner both use this ingredient at 5–10% — the upper functional range. Every ingredient at the concentration where it performs, not at the concentration where it can merely appear on the label.
Common questions
Is fermented rice water good for hair?
The evidence is real but narrow. Fermented rice water is rich in inositol, a carbohydrate small enough to penetrate the hair shaft rather than sit on its surface, and the available research links it to improved resistance to mechanical stress — what is commonly meant by “strength.” That evidence base is small, not large, so we grade this benefit supported, not well established. It is not a substitute for structural repair, and we would not claim it affects growth or thickness — the current research does not support that.
Is fermented rice water actually better than regular rice water for hair?
Yes, for one specific reason: fermentation. Plain rice water contains many of the same compounds as the fermented version, but at lower concentrations and in less bioavailable forms. Fermentation breaks larger molecules down into the smaller form of inositol that can penetrate the hair fibre, and it lowers the pH of the liquid — which helps close the cuticle and adds shine. Unfermented rice water isn’t harmful, it’s simply a weaker version of the same idea.
How is fermented rice water used on hair?
Traditionally as a rinse — often after a bồ kết wash — left on for a few minutes and then rinsed out, to avoid protein build-up over time. In our Botanical Scalp Shampoo and Rice Water Conditioner, we use Oryza Sativa Ferment Filtrate at 5–10%, the functional concentration range for rinse-off products — formulated so you don’t need to ferment your own.
Which hair types benefit most from fermented rice water?
Fine, limp or low-density hair tends to benefit most. Inositol helps hair feel stronger and fuller without the heavy coating oils and butters can leave, so it adds body rather than weight. Thick, dry or curly hair usually needs more nourishment than rice water alone provides — which is where coconut comes in.
How much fermented rice water is in Maison Bạch products?
We use Oryza Sativa Ferment Filtrate at 5–10% in our shampoo and conditioner — the functional range in which it can contribute meaningfully, rather than a trace amount added for the label.
INCI: Oryza Sativa Ferment Filtrate · EU Status: Approved · No restrictions · Usage: 5–10% rinse-off · Addition phase: Cool-down <40°C
Related reading: Rice water or coconut — why one conditioner is always a compromise