My dog has a fear of flying insects. How do I help him relax?

I'm assuming my dog has recently been stung by a bee or anything with a stinger. It doesn't matter if it's a fly. If it flies and he hears the buzzing sound of them flying around, he will automatically go into panic mode. He can be in the middle of playing and stop. He'll either hide under your chair or jump right into your lap. He looks around with huge puppy-dog eyes, shake and sometimes whine. If they get close to him and he's feeling brave, he'll snap at them. I've tried to tell him it'll be alright, rub him and swat whatever he's watching. But he still panics. What can I do to ease his anxiety?