What Is Kurumi Kaku?
Kurumi Kaku is the cosmetic name for finely ground walnut shells sourced from two walnut species, Juglans mandshurica and Juglans regia. After the nuts are harvested for food, the empty shells are washed, dried then milled into small, uniform particles. These particles are mostly made of cellulose and lignin, the tough fibers that give the shell its strength, with traces of natural walnut pigments and oils.
People have relied on crushed walnut shells for centuries to scrub cookware and polish wood. In the 1970s formulators noticed the same gentle scouring action could lift dull surface cells from skin, so the material made its way into early face and body scrubs. Today manufacturers sift the powder through precise screens to control grit size, ensuring it feels smooth enough for cosmetic use while still offering noticeable polishing power.
You will usually see Kurumi Kaku in rinse-off products such as facial scrubs, body polishes, foot scrubs, exfoliating cleansing bars and certain shower gels. It also appears in microdermabrasion creams sold for home use when a brand wants a plant-based alternative to synthetic beads or salts.
Kurumi Kaku’s Cosmetic Benefits/Uses
This ingredient brings a single, well-known benefit to a formula.
- Abrasive: The hard yet rounded particles work as a physical exfoliant that buffs away dead surface cells, helping skin feel smoother and look brighter. By clearing built-up debris it can also allow moisturizers or serums applied afterward to sink in more evenly.
Who Can Use Kurumi Kaku
Finely milled walnut shell suits most normal, combination and oily skin types that can tolerate a bit of manual polishing. People with very dry, easily inflamed or reactive skin such as those who struggle with eczema, rosacea or active breakouts may find the grit too stimulating and could experience redness or a stinging sensation. On thicker areas like elbows, knees and feet almost everyone can benefit from its buffing action.
Because Kurumi Kaku comes from plant shells with no animal processing it aligns with vegan and vegetarian lifestyles.
Pregnant and breastfeeding women can generally use products containing Kurumi Kaku as it is not absorbed into the bloodstream, however this is not medical advice and anyone who is expecting or nursing should check with a doctor before adding a new product just to be safe.
The ingredient does not increase photosensitivity so it will not make skin more prone to sunburn. It also plays well with most leave-on actives because it is rinsed away after use.
Potential Side Effects/Adverse Reactions
Responses to topical Kurumi Kaku vary from person to person. The points below describe potential side effects that are possible yet unlikely for the average user when the product is formulated and used correctly.
- Skin irritation or micro-tears if the powder is too coarse or applied with heavy pressure
- Redness, burning or tightness in very sensitive or compromised skin
- Allergic reaction in individuals with a walnut or tree nut allergy due to residual proteins
- Excess dryness or flaking from over-exfoliation, especially when combined with other scrubs or acids
- Broken capillaries or worsened rosacea when used aggressively on thin facial skin
- Eye irritation if particles accidentally enter the eyes during rinsing
If any undesirable reaction occurs stop use immediately and consult a qualified healthcare professional or dermatologist for guidance.
Comedogenic Rating
Rating: 1 out of 5
Kurumi Kaku is made of hard, fibrous walnut shell with no oily residues so it does not sit on skin or melt into pores the way rich butters or waxes might. Because the particles are rinsed off after a short contact time the chance of pore blockage is very low, earning it a near non-comedogenic score.
Most people prone to acne can use it without new breakouts, though over-scrubbing may inflame existing blemishes which can make them look worse.
As a dry powder it does not feed surface bacteria or alter sebum chemistry, so it will not promote comedones on its own.
Summary
Kurumi Kaku acts as a natural abrasive that lifts away dead cells and surface debris, leaving skin smoother and brighter while helping subsequent products absorb evenly. It achieves this through tiny, hard particles that gently polish the outermost layer when massaged then wash off cleanly.
The ingredient enjoys moderate popularity in scrubs and microdermabrasion creams, especially among brands looking to replace plastic beads with plant-based options. It is less common in high-end facial care where many companies now favor chemical exfoliants but still has a loyal following in body care and foot products.
Overall Kurumi Kaku is considered safe for topical use when milled to cosmetic grade and used with light pressure. As with any new skincare ingredient it is wise to do a quick patch test before full application to ensure personal tolerance.