Is BBL laser for hyperpigmentation safe on someone with dermographism and hives? How many passes are common?

Hope all is well with you. I've never been a sunbather; I avoid it. I'm a Fitzpatrick 2 with some hyperpigmentation from time, age, hormones, life in general. Is it safe to do BBL if I have dermographism and chronic hives? Both are well controlled with half a Xyzal daily. Also, what is the typical number of passes that are done over the face per treatment? Is it just once or multiple? I'm afraid of getting burned. This would be done at a Derm or Plastic Surgeon's office, NOT a med-spa!