Hi Anne. How long has he had symptoms? To me it sounds like he has more going on than just Bell's Palsy. Many people are bitten without knowing it, and only about 50% of people who have Lyme ever get a rash. I think he should be evaluated by a Lyme knowledgeable doctor to rule out or confirm Lyme.
Please know that steroids are not good for people who have Lyme. They suppress the immune system and can make Lyme symptoms worse.