I have a case of poison oak on my face. should i take prednisone pills or use just creams?

Depends on severity: Prednisone and the more potent steroid creams need to be prescribed by your doctor, anyway; have your doctor evaluate your rash and follow the advice with regard to how aggressively it should be treated.

Can use either: As dr. Steven said, it depends on how widespread it is. If it is only a few spots, a cream is fine. If you use a cream on the face, you have to be careful not to use it too long, especially if it is a high potency cream.

Probably pills: For more severe poison oak contact dermatitis even prescription strength steroid creams are not sufficiently effective. I recommend fairly aggressive use of Prednisone to get symptoms under control, and continue therapy for at least 7 to 10 days (as taper) to avoid rash recurrence.