Fibres Under The Microscope – What’s Itchy? What’s Not? Why?

It’s not hard to predict which sweater or scarf will be itchy when you see fibres under the microscope.

Here are a few details about the significance of the scales that you can see and the absence of them, on protein, plant, and synthetic fibres.

Protein Fibres

Animal fibres have scales that protrude; the larger the scales and the more they stick out, the itchier the fibre will feel. Alpaca and cashmere, with smoother, flatter scales are the easiest to wear of the animal fibres.

Sensitivity to animal fibre may be due to those scales or can be caused by a sensitivity to lanolin, found in wool.

Silk worms extrude a single length of scale-free fibre, hence, no itch.

Plant Fibres

The plant fibres, linen and cotton, are free of scales, but linen, made from the flax plant’s stalk, can feel harsh to wear at first. It softens when washed. Cotton, made from the downy fibres of the cotton boll, is comfortable to wear.

Synthetic Fibres

Synthetic fibres, like acrylic and polyester, are chemically created, liquified and exuded in continuous fibres on machines. There are no scales to cause itching, but synthetics have less breathability than the nature-made fibres.

Choose carefully if itchy yarns bother you. Years ago a knitting teacher recommended tucking a bit of a fibre into your bra to test sensitivity to it, but I’ve heard since that the neck is a better testing site. Not easy to do when you are standing in your favourite yarn store, smitten with a yarn, so information on the ball band is your friend. What is in that yarn?





5 Replies to “Fibres Under The Microscope – What’s Itchy? What’s Not? Why?”

  1. This is absolutely fascinating! I want to see more on the technical side of things. Those of us who don’t make still wear! Thank you for going after this information, Gayle!

  2. I admit to often rubbing fibre or yarn gently on my neck in shops. I don’t care who’s watching!
    Your pictures are interesting, but there are other elements besides the scales in the itchy problem. A lot of the prickle comes from the ends of fibres, so stiffer fibres are apt to cause itch. And if a fibre is stiff, the more ends the more itch – so yarns made from shorter fibres are pricklier.
    That is sometimes suggested as a reason to spin locks of wool from the tip, not the cut end, because then the prickly cut ends get buried in the centre of the yarn. I don’t know whether there’s anything in that.

    1. So intersting. I am teaching a fibre class today and I’ll add the fibre end topic to our discussions about wool.

  3. If you want to get a bit more technical, for wool there’s also a thing called the coefficient of variation (CV). You might have two Merino fleeces, both graded as (say) 16 micron. But that’s the average thickness of the fibres, and the CV is the spread of fibre diameter. One fleece might have all its fibres very close to 16 micron, and the other might have quite a lot that were much finer or coarser. Those coarser fibres are going to make the second one feel more prickly than the first fleece with the low CV.

    The moral of that for a spinner or knitter is to choose wool by how it feels to you, and not just by the label. The moral of it for a sheep breeder trying to produce the very top quality wool is to get fleece samples objectively measured and include CV in selection criteria. The principle is “Finer wool is not better wool unless it is also less variable”.

  4. Thank you for adding so much richness to this discussion. It’s clear the CV is really important and yet so very nice to know that how yarn feels to us as spinners and knitters is the important thing.
    Thank you.

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