To remove mildew from leather jackets, air the jackets out, then use cleaners before applying a fresh coat of conditioner. If this does not work, take it to a dry cleaner.
Leather mildews when oils and conditioners are too thick to let it breathe. Being tightly packed in a closet or trunk also causes leather to mildew.
Step 1: Let it breathe
Hang the jacket somewhere warm with air moving around it. Leave it there for a few hours or a day.
Step 2: Use cleaner
Mix 1 cup water and 1 cup rubbing alcohol, then rub it in with a soft cloth. Let it dry completely.
Step 3: Cleaner and conditioner
Apply a thin coat of moisturizing leather cleaner-conditioner all-in-one product and buff the leather off with a clean cloth.