Kojic acid alone has never been proven to lighten pigmentation. It is a supplement in many products with hydroquinine as well. Some people have the opposite reaction to lighteners! If you are using a hydroquinine and have no results in a month-and do not expect spots to dissapear completely-stop using he product. Also, stay out of the sun because lightened skin burns even more quickly, and repigmentation is even worse.
If you use sunscreen and are outdoors and not reapplying ever 2 hours, its best to skip the sunscreen. Most sunscreens (not zinc based) degrade within 3 hours and invite free radicals below the surface of your skin!
Fruits and vegetables are antioxidants which fight free radicals, but they are not a sunblock.
Pregnancy,menopause, the pill,etc can cause hyperpigmentation in some women.