Infrared Clothing: A Buyer's Guide to How It Works and What to Buy
Infrared clothing is clothing made with fiber that absorbs your body heat and re-emits it as far infrared energy. It has no battery and no heating element. ACCAPI's fiber emits in the 5–20 micron range, and the research on it is early but real. This guide explains how it works, what the evidence does and doesn't show, and which type to buy for how you'll wear it.
How infrared clothing works
The yarn is engineered with materials that take in thermal energy from your body and send it back toward your skin as far infrared. Nothing is switched on or charged. The effect depends on your own body heat, which is why it works the same in a sock on your feet or a baselayer on your torso.
Not every infrared fiber is the same. The wavelength it is tuned to and whether a lab has measured it make the difference. ACCAPI's fabric is KIFA certified (KFI-588) with a measured emissivity of 0.890. For the technical side, see our core fiber technology page and infrared fibers explained.
What infrared clothing is not
- Not heated clothing. No battery, no heating element.
- Not red light therapy. That uses an external light source. See Red Light Therapy vs. Wearable Infrared Clothing, and whether red light works through clothing.
- Not the same as compression. Some infrared products have light compression and some, like Sleep Socks, have none. See Infrared vs. Compression Socks.
What the research shows
The evidence is narrow and early, and anyone who tells you otherwise should show you the study.
- A 2023 study in Life (Bertuccioli et al., PMID 37895379) found a 6.7% reduction in body resistance and a 5.4% reduction in reactance in trail runners wearing FIR garments. These are bioimpedance markers, and the study was small.
- A 2025 sleep study of 30 people reported better sleep scores with ACCAPI Sleep Socks. It had no control group, so the results can't be credited to the socks alone.
The fair reading is that the fiber does something measurable, and evidence for specific benefits is still developing. The full breakdown is in Does Infrared Clothing Actually Work?
Is it safe to wear every day?
ACCAPI's fiber was tested under ISO 10993 for cytotoxicity, skin sensitization and irritation, and tested for harmful dyes and formaldehyde. The results and report numbers are in Is Infrared Clothing Safe? If you have a medical condition or a known material allergy, ask your doctor first.
Which infrared clothing should you buy?
| If you want | Look at | Good to know |
|---|---|---|
| Everyday, travel or training socks | Energy Wave socks | Light compression plus infrared fiber. From $39.95. Guide |
| Something to sleep in | Sleep Socks | Loose-fit merino wool, no compression. $59.95. Is it okay to sleep with socks on? |
| Training and recovery baselayers | PRO baselayers | Shirts and tights with FIR fiber. Passive recovery |
| Training apparel | Health Power | FIR training apparel. Study |
| Support for a specific joint | Bodyguard supports | CE Class 1 medical devices, HSA/FSA eligible. Buyer's guide |
| Skiing | Infrared ski socks | All four ski sock lines use infrared fiber |
Not every ACCAPI baselayer is an infrared garment. The Polar Bear, ErgoRacing and Xperience lines are built for warmth, racing and balance, and they don't use FIR fiber.
See the fiber in the products
ACCAPI has put this fiber into socks and baselayers since 2008. Pick the one that matches how you'll wear it:
Browse all infrared recovery →
Frequently asked questions
What is infrared clothing?
Clothing made with fiber that absorbs the heat your body gives off and re-emits it as far infrared energy. ACCAPI's fiber emits in the 5–20 micron range. There is no battery and no heating element.
Is infrared clothing the same as heated clothing?
No. Heated clothing uses a battery and a heating element. Infrared clothing has no electronics. The fiber works with the heat your body already produces.
Is infrared clothing the same as red light therapy?
No. Red light therapy uses an external light source. Infrared clothing is passive and depends on your own body heat. We compare them in Red Light Therapy vs. Wearable Infrared Clothing.
What are the benefits of infrared clothing?
The research is early. A 2023 study in Life measured changes in two bioimpedance markers in trail runners wearing FIR garments, and a 2025 sleep study of 30 people reported better sleep scores. Both are small, and neither proves a specific benefit. The details are in Does Infrared Clothing Actually Work?
Who is infrared clothing for?
People who want something passive to wear: athletes between sessions, people on their feet all day, and people who want a comfortable sock or baselayer for overnight or everyday wear.
Is it safe to wear infrared clothing every day?
ACCAPI's fiber passed independent skin-safety testing under ISO 10993, and no harmful dyes or formaldehyde were found. See Is Infrared Clothing Safe? If you have a medical condition or a known material allergy, ask your doctor first.
How do I choose the right infrared clothing?
Start with how you'll wear it: socks for everyday wear, travel or training; loose-fit socks for sleep; baselayers for training and the hours after; support garments for a specific joint. The table above matches each use to a collection.
Related reading
- Does Infrared Clothing Actually Work? What the Research Says
- What Is FIR Technology? Far Infrared Fiber Explained Plainly
- Far Infrared Compression Socks: What They Are and Who They're For
- Is Infrared Clothing Safe? The Biocompatibility Story
- How to tell if infrared clothing claims are real
