Dirt and body oils will contaminate the down causing it to clump together and lose loft. Dirt also attracts water and reduces the beading-up of droplets on the fabric's surface. Wash the garment in Nikwax Downwash non-detergent soap. Detergents can leave water-attractive residues that will not rinse out. They also contain agents that can wash away the natural oils of the down.

Nikwax Downproof is a wash-in product that will treat the whole garment or sleeping bag with a durable water repellency (DWR) that does not affect breathability, look or feel.