Why do sweaters pill, and can you prevent it?
Pilling is loose fiber ends tangling under friction. Longer fibers and tighter knits pill less; a fabric shaver fixes what forms.
Pills form where fabric rubs - under arms, where a bag strap crosses, against desk edges. Short-staple fibers (cheap cotton, acrylic, low-grade cashmere) have more fiber ends per inch, so they pill fastest; that is why a $30 acrylic sweater looks tired in a month while a long-staple merino stays smooth. Prevention: choose tighter knits (hold to light - less see-through is better), wash inside-out in a bag, and never hang wet knits. Treatment: a fabric shaver or sweater stone removes pills cleanly; do not pull them by hand, which yanks more fiber loose. A sweater that pills heavily in its first two wears was badly made and will not improve.