There is nothing worse than pulling your laundry out of the dryer only to discover that you have accidentally put your favorite wool sweater through the dryer and it has shrunk. If you have a sweater that has shrunk, there is one thing you can do to try to unshrink it and bring it back to its true shape, although they do not always work depending on the exact fibre composition of the yarn. But it is always worth trying before you give it to the thrift store to fit someone three sizes smaller than you.
Fill the laundry tub or bath with a few inches of warm water and add a generous amount of hair conditioner. Gently work the solution through the entire sweater, kneading the sweater as you go. Pull it out of the water and place on a stack of bath towels (since the sweater will be soaking wet) and then gently stretch the sweater into the former shape. Allow to dry in a cool room – DO NOT use any heat to dry the sweater. Repeat if needed. Then wash again as usual, being sure to rinse fully to remove the conditioner, and lay flat to dry.