Is Merino Wool Itchy?
No, not if the wool is fine enough.
Prickle is caused by fibers coarser than roughly 22 micron. Those are stiff enough to press back against your skin instead of bending with it, and your nerve endings read that pressure as an itch. Wool spun finer than that threshold bends, and the sensation never starts.
What micron actually measures
A micron is one thousandth of a millimetre, and the number describes the average diameter of the fibers in the yarn. Lower is finer. Ordinary wool, the kind in a scratchy jumper you remember from childhood, typically runs 25 to 40 micron. Merino is a different breed of sheep with a far finer fleece, generally 15 to 24 micron.
The useful statement, then, is not "wool itches" or "merino does not." It is that fiber diameter decides, and merino is usually fine enough to sit on the right side of the line.
Where the reputation came from
Most people who believe wool itches are remembering a coarse wool garment, not a fine one. The fiber they are thinking of and the fiber in a merino base layer have almost nothing in common except the word.
How to check before you buy
Look for a published micron count. Anything at or below 19.5 is comfortably inside the range most people wear against skin all day. Between 19.5 and 22 is fine for most people and marginal for a few. Above 22 belongs over another layer.
If a brand does not publish the number, that is worth noticing. Micron is the single most useful specification for wool, and it costs nothing to print.
One thing that is not prickle
A small number of people react to lanolin, the natural wax in wool, rather than to fiber coarseness. That is a genuine sensitivity and it is different from the prickle effect described above. Most processed merino has very little lanolin left in it, but it is worth knowing the distinction if fine wool has bothered you before.
Where ours sits
Our next-to-skin line is 100% merino spun to 19.5 micron and knit to 135 gsm. Every product page states both numbers.