You have to really make sure borax is fully rinsed out or it can leave some residue as well. But, it can be extraordinarily effective at cleaning clothes, particularly if you 1) fully dissolve it in water prior (use boiling) and 2) soak for at least an hour.

Borax is also effective at killing mold. But, like you innormally stock with vinegar. Gets rid bacteria, viruses and mold too.