Why doesn't merino wool itch?

This is due to the fiber strength of the merino wool. Merino sheep belong to the breed of fine wool sheep, their fur consists of very finely curled hair. Depending on the quality of the wool, the fiber thickness is only 16 to 24 microns (microns = thousandths of a millimeter), which is very small. For comparison: conventional sheep's wool is usually twice as thick and the hair on our heads is even up to four times thicker than that of merino wool. Whether a wool itches and scratches depends on the human itch threshold, which starts at around 25 microns. Of course, the sensitivity threshold varies from person to person. The finer a fiber, the more it bends when it touches the skin. Thicker wool fibers do not wrinkle and literally prick the skin, causing it to become irritated and perceived as unpleasant scratching and itching. This is not the case with merino wool, with up to 40 bends per centimeter it is perceived as pleasantly soft on the skin.