Sweaters are often made from wool or other loose fibers that can be easily contracted in heat. If a sweater is accidentally left in a load of regular laundry, it may shrink so much that it becomes unwearable. While there is no guaranteed method for resizing a shrunken sweater, don't run out and purchase a new one until you've tried to unshrink it. There is a simple solution that will allow you to expand your sweater, in the hopes of making it wearable once again.
Lay a thick bath towel out on the floor of the bathroom.
Fill your bathtub will lukewarm water and add 2 tablespoons of hair conditioner or baby shampoo to the tub. Mix well.
Add the sweater to the tub and let it soak for about 15 minutes.
Drain the tub. Remove the sweater, allowing excess water to drain from it but do not wring it dry.
Lay the sweater out on the dry towel. Pull on various areas of the sweater to stretch it back out to its normal size. Remember to stretch the collar and wrist areas too.
Return to your sweater periodically (every couple hours or so), stretching it back to its original shape. Continue to do this until it has completely air dried. When it has dried, your sweater should be expanded back out.