Blisters/boils around dog mouth

Question
My cocker developed blisters and some rather larger ones around her mouth.  She was uncomfortable last night but eventually fell asleep...can you tell me where they came from or what they are?

Answer
My first thought was, "What did that dog get into?" Do you have any poisonous/toxic plants in the yard or house that she could have chewed on? http://www.ansci.cornell.edu/plants/index.html

The next thought is that it could be an autoimmune problem. If this doesn't go away in a few hours or she worsens, get her into the vet as soon as possible.