It all depends on what kind of sweater you're thinking of-
knit sweaters are made of wool or yarn (i think)
some are made of cotton, and polyester, and 100% rayon (probably)
You should look it up!
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"Polo sweaters can be made from a variety of fabrics. Men's sweater are typically made from a blend of wool and cotton while women's sweater tend to be cashmere. However, depending on the label, the...