@burcidi-- I agree with @ankara. I'm sure everyone's skin reacts differently to different exfoliating brushes. But I have a sisal loofah face brush and I use it every morning and evening. I have not had any irritation or pain from it. It's really gentle.
Regardless of whether you are using a sisal brush or a loofah, make sure that you are using it for the right body part. A sisal body brush can be too harsh for the face and a sisal face brush would not exfoliate the body enough. Both of these are made of sisal fibers but they are processed and shaped differently depending on what it's supposed to be used for.