You may clean many wool items, such as sweaters, in a washing machine if you use a detergent that is specifically suitable for wool. If it doesn’t say so on the label, find something that is. The acidic nature of woolen fibers makes them susceptible to damage by alkaline detergents, but wool-friendly products have a neutral pH of 7. Dirt-fighting enzymes in typical detergents also damage wool fibers, causing shrinkage and matting, while other detergents fade the dyes used to color wool.
If your washing machine has a wool or knit cycle, always use it when cleaning woolen clothing and never let the water temperature go above 104 degrees Fahrenheit. These cycles are use less agitation, preventing the fibers from taking on a felt-like texture, and don't alternate between cold and hot water, which causes shrinking. Wash fewer wool items at a time for the best results, filling the machine to roughly half its normal capacity.
Many woolens are easily cleaned by hand, which is gentler than placing them in a washing machine. Simply fill a sink with tepid water that's comfortable to touch and a portion of wool-safe detergent made for hand washing. Swish the item around carefully before leaving it to soak for a few minutes. Carefully rinse it to remove any remaining grime and suds.
After washing, remove excess moisture from your woolen item by placing it flat on a clean towel and gently rolling it up while pressing down to absorb water. Next, gently reshape it, closing any fastenings and giving extra care to details like collars and cuffs. Let the item lay flat on the towel, away from direct sources of light and heat, and leave it to dry, flipping it over periodically.