On the web some suggested to disconnect the negative battery terminal, sprayed down the alternator thoroughly with the MAF cleaner, and let it dry for about 10 minutes.
If you decided to do it, please make sure the engine is cold.
How much oil have you spilled on the alternator? Was it when you were changing your oil? Do you have a code warning on the dash that tells you that the battery is low..? Is the voltmeter indicate a low charging? All these questions are important to know before taking some actions.