Odors in sweaters and other clothing can be caused by a number of factors. Formaldehyde is often used to make fabric wrinkle-free. Fumigants and anti-mildew chemicals are sprayed on clothes prior to the trip from the factory to the store. Other smells, such as cigarette and campfire smoke, perfumes, deodorants and body odors can leave your clothes with a peculiar odor. If you're particularly sensitive to certain smells, especially chemicals, you may have a hard time wearing even the cleanest clothes, even though others may insist they smell just fine.
Air out your sweater. Hang it in a sunny room with a breeze. Surround it with plenty of green plants, which absorb volatile organic compounds, or VOCs, such as formaldehyde. Depending on the origin of the odor, it can take anywhere from a few hours to a few weeks for your clothes to lose the smell.
Soak the sweater for a few hours in a washing machine filled with warm water and one cup of baking soda, if your sweater is washable.
Wash the sweater according to manufacturer's instructions. Use a chemical-free detergent. Add a cup of white distilled vinegar to the rinse cycle.
Line-dry your sweater to further air it out. Sunlight aids in deodorizing fabric; if possible, hang your garment outdoors in the sun to dry.
Repeat Steps 2 through 4 until the odor has disappeared.
Always wash new clothes before you wear them to remove residual chemicals added during the finishing process and prior to shipping.