Merino Wool

The question people arrive with is whether merino will itch, and the answer is mechanical rather than allergic. A fiber coarser than roughly 30 microns is too stiff to buckle when it meets skin, so it presses into nerve endings instead; the trade measures this as prickle factor, the share of fibers in a sample above 30 microns, and above about 5% most wearers call the fabric prickly. Merino sits below that threshold in every grade, which is why it reads as a different sensation and not merely a softer one. The fiber itself is inert keratin with nothing to leach against skin. Two things do undercut a merino garment's plastic-free claim: most machine-washable merino is superwash, meaning it carries a thin polyamide-epichlorohydrin resin (see Wool), and socks and hard-wearing base layers are commonly blended with nylon or elastane, which sheds synthetic microfiber in every wash. The separate welfare question is mulesing, the removal of skin from a lamb's breech to discourage flystrike. It is not a fringe practice - around 70% of Australian graziers do it, a 2017 survey found 83% of mulesed Merino lambs received analgesia or anaesthesia, and the industry case for it is that flystrike would otherwise kill sheep in very large numbers. New Zealand banned it outright in 2018, so New Zealand merino is mulesing-free by law.

Merino never sees a hot path in use; it is a skin-contact fabric. What heat does to it is destructive rather than chemical - a hot wash or a tumble dryer felts and shrinks untreated merino permanently, and repeated high heat is the fastest way to wear out a lightweight base layer. Its fire behavior is the same as any wool (see Wool), which is a real advantage over a polyester base layer near flame.

Read the fiber content label, not the front of the garment: "merino" on a hangtag with "52% polyester" on the inside label is a common pairing, and "merino blend", "merino touch" and "wool-like" are marketing rather than fiber content. A brand that is proud of its wool publishes the micron number, so 17.5 or 18.5 on the product page is a good sign and silence usually means a coarser lot. Ask two questions directly: is the wool superwash or otherwise shrink-resist treated, and is it certified non-mulesed. Against acrylic, the burn test described on the Wool page settles it in seconds.

Wash cool and gentle and line dry - the tumble dryer is what kills merino, and surviving one is much of what people are buying when they buy superwash. Air merino out between wearings instead of washing it, which is what the odor resistance is for. Lightweight base layers wear through first at shoulders, pack straps and heels, which is precisely why nylon gets blended in at those points. Store it clean and sealed, because moth larvae treat it like any other wool.

Untreated, unblended merino biodegrades in soil like any wool. A superwash garment carries a resin that does not, and a nylon-blend sock is a composite that will neither compost nor recycle. Merino is thin and high-value enough that resale and brand take-back schemes are the realistic second life; nothing about it is curbside recyclable.