Merino wool: benefits and limits for outdoor clothing

Merino wool is one of the most versatile materials for outdoor use. It regulates body temperature, resists odour naturally and feels more comfortable on the skin than many synthetic fibres. But the natural fibre has its weaknesses too. We look at who merino suits, and where alternatives do better.

Merino wool is more than a trend. A whole range of properties makes it hard for outdoor enthusiasts to do without. One of the biggest is its excellent thermoregulation. The fine fibres trap a lot of air and form an insulating layer. So it keeps you cosy in winter and has a cooling effect when temperatures rise. That matters most in changeable weather or during hard exercise, because it helps keep your body at its ideal operating temperature.

Another plus is moisture management. Merino fibres can absorb up to 35% of their own weight in moisture without feeling wet. The moisture then moves slowly outwards, so your skin stays dry and you do not get chilled, an important factor in preventing colds. The wool's breathability also stops uncomfortable heat build-up.

Fine merino at 16.5 microns is among the softest varieties, and in high-quality blankets it reaches fabric weights of up to 1,000 g/m², which shows how well it insulates.

After a hard day out, synthetic clothing can quickly start to smell. This is where merino plays its next card: it is naturally odour-resistant and antibacterial. The complex surface of merino fibres makes it harder for odour-causing bacteria to cling on and multiply. You can wear merino clothing for several days before it starts to smell, which is ideal for multi-day treks or travelling light. This property also makes it interesting for allergy sufferers, as it reduces mite reproduction.

Merino also scores on comfort. Unlike conventional wool, it does not itch. Its fibres are so fine and soft, often under 19 microns, that they feel gentle on the skin. That makes it a perfect choice for underwear and baselayers worn right next to your body. The wool's elasticity and shape retention mean clothing keeps its fit after frequent wearing and washing instead of stretching out. Many manufacturers, including Engel and Woolville, stress the 'highest quality' of the temperature-regulating and odour-resistant properties of their merino products.

For all its strengths, merino wool has a few points to weigh up before you buy. The most obvious drawback is the higher price compared with synthetic alternatives. The demanding production and processing of the fine fibres, plus the high animal welfare standards many manufacturers now meet, are reflected in the price. For many people, though, the durability and performance make it worth the investment.

Another point is care. Merino wool is more delicate than synthetic fibres. It reacts to high temperatures, strong friction and certain detergents, and the wrong care can cause shrinking, felting or fibre damage. Even though modern merino products are often machine washable, they still need more attention. A knitting expert from JoelJoel, for example, warns that knitting too tightly or using needles that are too small can make merino feel 'like a board' and lose its fluffiness. It shows how much correct handling matters for keeping the material soft.

Merino wool is hard-wearing, but not indestructible. Compared with robust synthetic fibres, it is less resistant to abrasion and wear. Pilling or thin patches can appear sooner, especially in high-stress areas such as under rucksack straps or in the armpits. To counter this, many manufacturers use blends. Adding fibres such as nylon or Tencel increases durability without taking too much away from merino's strengths. These hybrid products combine the comfort and thermoregulation of wool with the toughness and longevity of man-made fibres.

Sourcing can also remain controversial in some circles, despite high animal welfare standards such as mulesing-free production. That is one reason recycled wool is becoming more popular: no new fibre has to be produced for it. And although merino is very kind to the skin for most people, some allergy sufferers react to wool in general and need to choose alternatives.