What Causes Blisters On Face?

my sister is breaking out with blister like open soares on her face. She has been to every determatolgist in the our City and they have not been able to help her. She also went to an infectious disease doctor and all they have done is rule out that she does not have lupus, aids, chingles, arthritis. They have done several cultures and they come back with high levels of bacteria. The antibiotics work while she is on them. As soon as she gets off them they blisters come back. She states she feels her face is on fire and extremily itchy. The sores do have drainage. When they dry up it looks like she has burns on her face. The episodes are occurring more frequently now to where it is affecting her daily life. The sores are only to her face, therefore, the doctor s do not feel that is an allergic reaction as it is locolized to her face. Last week she had severe, uncontrolled itching to her legs. The following day she developed bruising as if she had been attacked. We are are desprate and don t know what else to do. What other type of doctor should she see? Please help. Marisela Galindo