"IN CLINICAL TRIALS OF BIPOLAR AND OTHER MOOD DISORDERS, THE RATE OF SERIOUS RASH WAS 0.08% (0.8 PER 1,000) IN ADULT PATIENTS RECEIVING LAMICTAL AS INITIAL MONOTHERAPY AND 0.13% (1.3 PER 1,000) IN ADULT PATIENTS RECEIVING LAMICTAL AS ADJUNCTIVE THERAPY."

http://www.rxlist.com/cgi/generic/lamotrigine.htm

So, not very common. The reason that you see so much about this rash is that it can be extremely serious, even fatal, in very rare cases. this is also why why you titrate the dosage so slowly when you begin therapy...it reduces the chances of this rash occurring.

DJ