 T-shirt yarn is a yarn made directly from t-shirts, and the fiber composition is determined by the material the t-shirt is made from.In general, natural fibers tend to require more careful handling than synthetics because they can shrink, felt, stain, shed, fade, stretch, wrinkle, or be eaten by moths more readily, unless special treatments such as mercerization or superwashing are performed to strengthen, fix color, or otherwise enhance the fiber's own properties.Some types of protein yarns (i.e., hair, silk, feathers) may feel irritating to some people, causing sensations of contact dermatitis, hives, wheezing reactions.