Our warm HOCOSA Kids’ / Children’s long sleeve undershirt with a Round neckline in smooth fine knitted organic merino wool knit that doesn’t itch. Made out of 100% certified and breathable organic merino wool. Soft and breathable merino wool can be worn in every season. It breathes with the body, does not cause perspiration and provides warmth even when damp. Woolen underwear keeps the child warm during winter and is also good for a cool summer. Pure natural wool fibers are flexible and breathe even in warm weather. Care Instructions.