Wash inside out on a cool cycle at 30°C with a mild detergent, and only when they need it — airing between wears keeps them fresher than frequent washing does. Skip fabric softener; on fleece it flattens the pile and reduces how well the fabric traps warmth. Wash with similar weights rather than with towels or denim, which are abrasive and speed up pilling.
Line dry or dry flat, and keep them out of the tumble dryer — heat mats fleece pile and shrinks cotton-blend jersey through the body and sleeves. If a garment does need pressing, use a cool iron and avoid any printed or embroidered areas. Pilling on the cuffs and under the arms is normal wear on any soft knit or brushed fabric, and comes away easily with a fabric shaver.
A washing bag designed to catch microfibres is worth using on synthetic fleece — it reduces what ends up in the water and is gentler on the garment at the same time.
