Washi Paper Changed Sports Socks! Itoix Realizes a Stuffiness-Resistant Structure

For long-distance runners, sweaty, stuffy feet are an inevitable problem. When sweat and heat get trapped inside shoes, socks cling to the skin, and the spaces between toes become sticky. Getting wet from rain or puddles only worsens the discomfort, leading to blisters and odors.

Itoix's "Running Socks" tackle this foot moisture problem head-on using traditional Japanese paper (washi) material. Made primarily from washi fiber derived from Manila hemp, its porous structure easily absorbs, disperses, and releases moisture.

The fact that these socks are chosen by ultra-runners and Self-Defense Forces personnel who wear boots for long hours is proof that they deliver performance under harsh conditions. Why can washi socks keep feet comfortable even in extreme environments? We asked Takuya Shagawa, CEO of itoix Co., Ltd.

Pursuing "Stuffiness Resistance" Led to Traditional Washi Paper

Putting them on for the first time, what stood out immediately was how cleanly they sat against the skin—quite unlike standard sports socks. It's neither the soft, wrapping feel of cotton nor the sleek, slick texture of synthetic fibers. Instead, there's a unique crisp texture, with a subtle tactile feel under the soles.

Even when sweating during a run, the fabric hardly sticks to the bottom of your feet. Moisture doesn't easily linger inside the socks, leaving your soles feeling completely dry even after taking them off. This dry feel is precisely what defines Itoix socks.

"The key is not letting moisture stay trapped inside the shoe. When your feet get wet from sweat or rain, it causes not only stuffiness and stickiness, but also blisters and odor. That is where the properties of washi material truly shine."

Not Mere Paper, But Functional Fiber Derived from Manila Hemp

When people hear "washi," they tend to imagine thin, easily torn paper. However, Itoix uses a specialized washi fiber processed specifically for apparel.

The main raw material is abaca, a natural plant fiber also known as Manila hemp. It is lightweight yet strong and boasts excellent durability. Ultra-thin washi made from abaca is slit into narrow strips about 1.5 mm wide, twisted into yarn, and knitted into socks.

"We design them so that the washi yarn sits on the inside, touching the skin. That's what creates that crisp, dry tactile feel the moment you put them on."

However, since washi has less elasticity than typical fibers, it is difficult to craft directly into socks. Therefore, slitting the washi paper into tapes and twisting them imparts flexibility, processing it into yarn suitable for sock knitting.

That said, because washi yarn stretches little and managing tension during knitting is tricky, commercializing it requires factory expertise that deeply understands the material's characteristics. Only a limited number of factories can produce socks using this washi yarn.

Porous Structure Absorbs and Releases Moisture

Washi fiber derived from Manila hemp features a "porous" structure. "Porous" refers to a structure filled with countless microscopic pores on the surface and inside the fiber. Instead of letting moisture from sweat or rain stay in one spot, these pores disperse it across the entire fiber.

Another fascinating aspect is how the motion of running or walking itself helps expel moisture. Every time your foot strikes the ground, pressure is applied to the socks, and when your foot lifts, the pressure is released. This repeated action makes it easier for moisture dispersed within the fibers to move outward along with air flow.

"Rather than holding onto absorbed moisture, it releases it through movement. The porous structure manages the foot's moisture environment, delivering stuffiness resistance and a dry feel."

"Damp Feet" Can Cause Blisters and Odors

Moisture remaining on your feet is not just a matter of discomfort—it can lead to a serious drop in performance.

"Blisters while running occur easily when friction and moisture combine. When skin gets damp with sweat, it softens, making it prone to stress even from slight misalignment with shoes or socks. Repeatedly landing and kicking off in that state makes blisters form more easily."

What the company focuses on is not forcibly suppressing friction itself, but controlling the moisture environment that increases friction. By keeping feet dry, the skin is less likely to soften, maintaining a state where blisters are less likely to form.

"Moisture is also linked to odor. That is why we have had a third-party organization confirm our deodorizing performance against isovaleric acid gas, which is considered a key cause of foot odor."

Functionality Required in Harsh Environments

ITOIX socks have received feedback from ultra-runners and long-distance runners saying things like, "My feet stay dry even after running for a long time," and "I barely notice any stuffiness or stickiness."

This level of performance is also evident from the fact that they are sold at stores inside Japan Self-Defense Forces bases. Self-Defense Forces personnel often wear boots for extended periods during exercises or disaster relief operations. In environments where socks cannot be changed frequently, quick-drying properties and durability make all the difference to foot comfort. Being able to wear them for hours while minimizing stuffiness is one reason they are so highly rated even in such harsh conditions.

ITOIX applied Japanese paper (washi)—a material seemingly unrelated to sports—to athletic socks. The company's running socks are steadily gaining support as gear to keep feet comfortable, from runners to people working in demanding environments.