How Merino Wool Helps Prevent Air-Conditioning Sickness Through Natural Temperature Regulation

In late June, the sunlight outside feels like midsummer, yet the moment you step indoors, the cold air from the air conditioner can make your body tense up. This is the season when drastic temperature differences continue throughout the day.

```

Feeling heavy in the afternoon, unusually cold around your feet, or suddenly chilled when sweat cools under the air conditioner — these may be early signs of “air-conditioning sickness.” For those who have tried putting on a cardigan or adjusting the air-conditioning temperature but still cannot solve the problem at its root, this article explains how to address it from the perspective of material.

HEALTH LOGIC Why Post-Sweat Chills Disrupt the Autonomic Nervous System

The main cause of air-conditioning sickness is “post-sweat chills,” which occur when sweat from being outside is suddenly cooled in an air-conditioned room. Cotton T-shirts absorb water well, but once they become wet, they dry slowly and continue taking heat away from the skin through evaporative cooling.

In response to this sudden change in body temperature, the brain constantly works at full speed to regulate body temperature. As a result, the autonomic nervous system becomes fatigued, leading to symptoms such as sluggishness, headaches, loss of appetite, and reduced concentration. You cannot always control the air-conditioning settings in the office. That is why protecting your body temperature with the material closest to your skin is the most rational solution.

MATERIAL COMPARISON What Does It Mean to Choose a Material That Does Not Make You Cold?

Clothes marketed as solutions for air-conditioning sickness are mainly divided into two types: cooling-touch materials and heat-retaining materials. However, neither properly addresses the essential cause of air-conditioning sickness: post-sweat chills.

Cooling-touch materials, often polyester-based, do feel cool the moment they touch the skin. However, once they absorb sweat, they can be slow to dry and continue taking heat away from the body indoors. Heat-retaining materials, such as fleece or thick knits, help prevent cold, but they can become stuffy outdoors and cause excessive sweating. Once indoors, that sweat cools down and creates a vicious cycle.

What is needed to prevent air-conditioning sickness before it starts is neither simply “cooling” nor “warming,” but rather moisture control that helps maintain a stable body temperature. Merino wool achieves this through a natural mechanism.

Material	Outdoors (Hot)	Indoors (Air-Conditioned)	Risk of Air-Conditioning Sickness
Cotton	Absorbs sweat and becomes stuffy	Stays wet and cools the body	High
Cooling-Touch Synthetic Fabric	Feels cool, but sweat remains	Continues taking heat away from the body	High
Fleece / Thick Knit	Becomes stuffy and causes heavy sweating	That sweat cools down	High
Merino Wool (General)	Controls moisture and releases sweat as vapor	Helps maintain moderate body temperature	Low
C-one Super 100's	Moisture control + non-itchy comfort	Temperature retention + suitable for business wear	Lowest

THERMOREGULATION SCIENCE Why Merino Wool Is Called “Natural Air Conditioning”

The core of merino wool’s temperature-regulating function lies in the “heat of sorption” generated when the fibers absorb moisture. In cold air, it releases warmth. In hot environments, it releases humidity and helps maintain coolness. This subtle heat exchange works to keep the “microclimate inside your clothing” — the space between your skin and the fabric — in a consistently comfortable state.

Cotton “holds sweat as liquid,” while merino wool “absorbs and releases sweat at the vapor stage before it becomes liquid.” This difference creates a decisive gap in how each material responds to air-conditioning sickness, even though both may be described as highly moisture-absorbent materials.

WHY C-ONE Why Not All Merino Wool Is the Same

At this point, you may be thinking, “I understand that merino wool is good. But wouldn’t a wool T-shirt from a mass retailer or a lower-priced brand work just as well?”

Moisture control is a common characteristic of merino wool. However, whether you can wear it every day in summer depends on the fiber diameter. The threshold at which human skin tends to feel itchiness is around 22μm. Merino wool that does not fall below this threshold can continue irritating slightly sweaty summer skin. Many commercially available wool T-shirts do not clearly state their fiber diameter, and some products exceed 22μm.

The Super 100's grade used by C-one has a fiber diameter of 18.5μm. This fineness, 3.5μm below the itchiness threshold, is the physical basis for the feeling of being able to wear it comfortably all day, even on sweaty summer skin. When choosing a material to help prevent air-conditioning sickness, it is not enough for it to have moisture control. It must also have a fiber diameter that stays comfortable even in summer.

In addition, while many wool T-shirts are available only in two or three colors such as black and gray, C-one offers a rich lineup of five to six colors for each style. It provides functional support against air-conditioning sickness while still allowing refined styling that fits naturally in business settings. This is one of C-one’s unique strengths.

```