Juice of a fresh lemon is acidic enough to safely peel off the upper layer of skin, which will remove or lighten some age spots.
Rubbing a piece of sliced red onion on age spots can have the same fading effect, since it has the same peeling acid as fresh lemon juice.
Applying castor oil twice daily with a cotton swab will sometimes bring about improvement.
Since age spots are caused by excessive sun exposure, avoid the sun and you’ll avoid age spots.