Sweat stains on underarms of whites

[QPootle]

Revolting I know, but does anyone know how to get them out without boiling them? There is a faint whiff as well. They've been there for some time ... is it time to ditch them?

Biotex spray BOTH sides, I have also changed my powder from Persil to Aerial for DH's shirts and have got most of them back to normal now. Spray every wash with Biotex to keep it at bay.