``I just washed it as usual and put it in the dryer, but my Heattech had shrunk to the size of a kid's size...'' ``The plastic parts in the dryer were melting!'' - Such complaints are often talked about on social media.

Actually, many clothes made from chemical fibers (polyester, rayon, polyurethane, etc.), including HEATTECH, are not compatible with dryers. In the worst case, it may lead to washing machine/dryer malfunction or fire. As of March 2026, UNIQLO's official website also states that HEATTECH is "not allowed to tumble dry."

In this article, we will explain in detail why you should not put heattech or synthetic fiber clothing in the dryer, and we will introduce Tips for safely and quickly drying.

Why does HEATTECH not use dryers in the first place? 3 reasons

UNIQLO's HEATTECH is mainly made from four types of chemical fibers: polyester, acrylic, rayon, and polyurethane. Each of these materials has a weakness against heat, and the following problems can occur in the high temperature environment of a dryer.

Reason 1: Rayon and polyurethane shrink due to heat

Rayon has the property of expanding when it gets wet and shrinking when it dries. When the heat of the dryer is added to this, the material shrinks much more than when drying normally. In fact, there is a report that ``M size HEATTECH shrinks to the equivalent of XS to S size after just one use of the dryer.''

Polyurethane (stretch material) is also sensitive to heat, and when exposed to high temperatures it loses its rubber-like elasticity and becomes tangled. Once HEATTECH shrinks or expands, it will not return to its original state.

Reason 2: Dryer parts melt due to abnormally high temperatures

Synthetic fibers such as HEATTECH may generate abnormally high temperatures during drying. There have been reports of cases where this heat melts the plastic parts inside the dryer, causing the plastic part under the washing tub to stick to its surroundings.

On social media, people are saying, ``My washing machine melted and broke'' and ``Heattech and other synthetic fibers reach abnormally high temperatures when drying, causing the plastic parts of the washing machine to melt.'' Please note that repair costs can cost tens of thousands of yen.

Reason 3: In the worst case, there is a risk of fire

The National Institute of Technology and Evaluation (NITE) has repeatedly issued warnings regarding accidents involving clothes dryers. In particular, when clothing with oil (kitchen mats, beauty salon towels, etc.) is placed in the dryer, the temperature of the remaining oil increases due to oxidation heat even after washing, leading to spontaneous combustion (NITE Product Safety Information Magazine Vol.334).

Although it is rare for chemical fibers to catch fire directly, it is important to remember that the material characteristics of easily trapping heat increase the risk of an accident.

How to tell which clothes can and cannot be put in the dryer

In order to answer the question, "Which clothes should I put in the dryer?", let's learn how to read the washing symbol. A new washing label (JIS L 0001) has been used since December 2016.

How to read the tumble drying mark

The "tumble dry" mark is a circle drawn inside a square.

  • Two dots inside the circle (...)→ High temperature drying below 80℃ is OK
  • One dot inside the circle (・)→ Low temperature drying below 60℃ is OK
  • X marked→ Tumble drying prohibited (no dryer)

If you look at the HEATTECH tag, you will see this "Do not tumble dry" mark. In other words, themanufacturer officially says, ``Do not put it in the dryer.''

Materials that tend to be rejected in the dryer

It is safer to avoid clothes that contain the following materials in the dryer.

  • Rayon: Expands with water → contracts with drying. Shrinks excessively in the dryer
  • Polyurethane: Loses its elasticity when heated and becomes like stretched rubber
  • Wool/Cashmere: Felts and shrinks hard
  • Silk: Heat and friction damage the fibers and cause them to lose their luster
  • Nylon: Easily deformed by heat. Wrinkles will not come off

On the other hand, clothes made of 100% cotton or 100% polyester tend to be relatively resistant to drying. However, be sure to check the washing instructions on the tag.

5 tips for drying quickly without using a dryer

It's understandable to worry that if the dryer doesn't work, your clothes will be half-dried. But it's okay. By combining the following methods, you can dry quickly enough even when drying naturally.

Tips 1: Dehydrate thoroughly

Set your washing machine for a longer spin time. With HEATTECH, dehydration for 3 to 5 minutes is sufficient. The less water there is, the faster it will dry. However, if you dehydrate it too much, it will wrinkle, so take it out as soon as you're done and reshape it.

Tip 2: “Towel dry” with a bath towel

After dehydrating, place HEATTECH on a dry bath towel, roll it up and press it lightly. The towel absorbs excess moisture, significantly reducing drying time.

Tips 3: "Hang dry inside out" in a well-ventilated place

The key to HEATTECH is to turn it inside out to dry. By placing the back side that touches the skin on the outside, it is easier to maintain the moisture absorption and heat generation function. Direct sunlight can cause fading and material deterioration, so it is best to stay in the shade with good ventilation.

Tip 4: Dry flat instead of on a hanger

Thin innerwear like HEATTECH may stretch under its own weight if you hang it on a hanger. You can prevent it from losing its shape by drying it horizontally using a flat drying net (you can also buy it at 100 yen shops).

Tips 5: Use a fan/circulator

When drying clothes indoors, just applying the wind from a fan or circulator will cut the drying time by more than half. When combined with the air conditioner's dehumidifying mode, it can also prevent dry room odors and kill two birds with one stone.

What if it shrinks in the dryer? First aid methods

If you accidentally put it in the dryer, unfortunately it is difficult to return it to its original size. However, if there is some shrinkage, you may be able to improve it by using the following methods.

Extend with lukewarm water + hair conditioner

Fill the wash basin with lukewarm water (about 30℃), dissolve a small amount of hair conditioner, and let it soak for about 15 minutes. The silicone in the conditioner coats the fibers, making them slippery and stretching them out a bit. After soaking, rinse it gently, shape it by gently pulling it with your hands, and then dry it flat.

However, this method is only a first aid measure. If it has shrunk significantly or the fabric has become stiff, you should consider replacing it. The manufacturer's idea is to treat HEATTECH as a consumable item and replace it every 1-2 seasons.

Three rules to remember to use the dryer safely

The dryer itself is a very convenient home appliance. To use it safely, please follow the following three rules.

Rule 1: Always check the washing label

When you buy new clothes, it is useful to take a picture of the washing instructions on the tag with your smartphone. You can check the tag even if you cut it off, and you can share it with your family when doing laundry.

Rule 2: Do not put oily clothes in the dryer

According to NITE's warning, clothing that has been contaminated with beauty oil, cooking oil, or animal fat may have oil remaining even after washing. Dry towels used in the kitchen or after a beauty treatment naturally, rather than using a dryer.

Rule 3: Clean the dryer filter regularly

If dust accumulates on the filter, the heat will not be exhausted properly and the internal temperature will rise, increasing the risk of malfunctions and accidents. Get into the habit of removing dust from the filter every time you use it.

FAQ

Will HEATTECH catch fire if I put it in the dryer?

Although the risk of HEATTECH alone igniting is low, there have been reports of chemical fibers generating abnormally high temperatures and melting dryer parts. It is also important to follow the washing label, as the risk of fire increases when combined with clothing that has oil on it.

Are dryers in coin laundry machines also prohibited?

Yes, the dryer at the coin laundry also uses tumble drying. The risk is actually higher because there are many items that are hotter than those used at home. Do not put HEATTECH or tumble dry clothing in the dryer, even at a laundromat.

Is it okay to use the "low temperature drying" or "home cleaning" mode of a drum-type washer/dryer?

Even in low temperature mode, the risk is not zero. As long as the manufacturer says ``Do not tumble dry,'' it is safe to avoid it even at low temperatures. If you really want to use it, use it for a short time (about 10 to 15 minutes) and take it out before it dries completely and switch to air drying.

What kind of clothes other than HEATTECH should not be put in the dryer?

Wool, cashmere, and silk clothing, elastic clothing (bras, swimsuits), decorative clothing (beads, sequins), and leather products are also prohibited in the dryer. Get into the habit of checking the washing label.

References