How to wash merino wool: shrinking, static and the right detergent

Wash merino wool at 30°C on a wool or delicates programme, using a wool detergent with a pH of 7 or below. Don't use fabric softener and don't tumble dry. Turn the garment inside out, use a laundry bag and choose the gentlest spin. Reshape the garment while damp and dry it flat. Most of the time no wash is needed at all — airing is enough, because merino wool cleans itself in fresh air.

Do you need to wash merino wool before wearing it?

No, you don't. Merino wool contains no irritating residues that would need washing out before the first wear. Every North Outdoor product is OEKO-TEX® STANDARD 100 certified, which means an independent testing institute has verified that it contains no substances harmful to health in skin contact.

An unnecessary wash only wears the garment out. With merino wool, a simple rule applies: the less often you wash, the better.

Does merino wool shrink in the wash?

The knit in a merino base layer shrinks by about 3–5 per cent in the wash. This is normal and expected, and it isn't a fault. The shrinkage is built into the sizing.

Gentle stretching while damp restores the garment to its original shape. If the base layer has stretched with wear, you can skip the stretching — the result is a better fit.

Uncontrolled shrinking is a different matter. It's almost always caused by too high a temperature, ordinary laundry detergent or a tumble dryer. The surface of a wool fibre has a scale-like structure, and heat combined with mechanical friction makes the scales lock into one another. The fibres tangle together and never come apart again — the garment felts. This cannot be undone.

What to do if a merino wool garment has shrunk

If it's mild shrinkage rather than actual felting, try this:

1. Soak the garment in lukewarm water for 10–15 minutes. You can add a dash of hair conditioner or wool detergent to the water to soften the fibre.
2. Press the water out; don't wring.
3. Lay the garment on a towel and gently stretch it back to size. Work gradually, in several stages.
4. Let it dry flat in the stretched shape.

The method helps with mild shrinkage. It won't rescue a felted garment.

Why does merino wool go static — and what can you do about it?

Merino wool is naturally anti-static, so static isn't a property of the wool but a sign that something else is off. The most common causes are dry indoor air in winter, a synthetic garment under or over the wool, and use of a tumble dryer.

What helps:

• Don't use a tumble dryer. It's by far the most common cause.
• Avoid synthetic layers directly against the wool — static builds up from two different materials rubbing together.
• Hang the garment in a humid room for a while, or lightly mist it with a spray bottle. Moisture discharges the static.
• Don't reach for fabric softener. It removes static momentarily but leaves a film on the fibre that permanently impairs the wool's moisture transfer.

How are different products washed?

Not all merino wool is washed the same way. The exact instructions are always on the garment's care label, but these are the main rules:

Nature knitwear should never be machine washed. The drum action and spin cycle loosen wool fibres and stretch the knit.

Why wool detergent rather than ordinary detergent?

Ordinary laundry detergents are alkaline. An alkaline solution clings to the wool fibre and weakens it: colours fade and bleed, the fibre roughens and over time the garment may develop holes. A roughened fibre also feels coarser against the skin than it did before washing — this is the most common reason a merino garment starts to feel itchy after a wash.

Wool detergent has a pH of 7 or below, so it doesn't damage the fibre. Fabric softener isn't needed at all, because merino wool is naturally soft and anti-static.

You'll find detergents and fabric shavers in our merino wool care selection.

Why is airing usually enough?

Merino wool is antibacterial. The fibre reacts with oxygen and evaporates odour molecules, including smoke and sweat. In practice this means the garment freshens up on its own when you hang it outside to air for a couple of hours.

A base layer stays fresh through a two-week trip without any trouble, as long as you air it after wearing. If the garment picks up visible dirt, there's no need to wash the whole thing — you can wash just the stain by hand.

Fewer washes save the garment as well as water and energy. Its antibacterial nature is therefore also an ecological one.

What about pilling?

When a wool garment is subject to friction, fibres come loose and gather into pills. This is in the nature of wool and isn't a sign of poor quality. Pilling decreases once most of the loose fibre has come away.

Use a fabric shaver regularly. Lay the garment on a flat surface and move the device lightly over the pills. Treat seams with care, and leave any snagged loops untouched. The largest pills can be picked off by hand.

For Nature knitwear we recommend a fabric shaver rather than a knit comb — using a comb too vigorously has been found to pull out an excessive amount of wool fibre.

Frequently asked questions

Can merino wool go in the tumble dryer?
Never. Heat and mechanical movement make the scales on the wool fibre lock together, which felts the garment irreversibly.

Can merino wool be ironed?
Yes, on the lowest heat setting. Steaming works too. Creases and fold lines come out easily.

How should merino garments be stored?
Folded, not on a hanger. A hanger stretches the knit at the shoulders.

Can merino wool be washed at 40°C?
We don't recommend it. 30°C is enough to clean it, and a higher temperature increases the risk of felting. Always check the garment's care label.

You'll find detailed product-specific instructions in our merino wool care guide. For textile care more broadly: clevercare.info.

North Outdoor is a Finnish company specialising in merino wool clothing. We design our products in Finland, and our own knitting mill is located in Oulu. We use only mulesing-free merino wool in our products.

Updated 13 August 2026