Lamictal tends to cause a benign
rash in 1/10 people, but the incidence of SJS (the really bad
rash) is around 1/3000, and the risk is higher in children and if you go up too fast. Some doctors are willing to retry it even if a rash developed the first time, taking it verrrrrry slowly (you can start in the pediatric range), especially if it was working really well for you before the rash appeared. Not all doctors (or patients) are willing to do this, though. Your mileage may vary.