The are may different products that claim to reduce oil. Vitamin B, Zinc, Evening primrose are some vitamins that are claimed to help.

However many people react differently. I find if i use a moisturiser/ sunscreen during the day i can reduce oil production quite a bit. Also dont excessively wash your face (max 2 times per day). Hope this helps, all the best. PS there is an 'oily skin' forum which could be more specific to your problem. All the best