I did a quick look at www.wikipedia.org, and with what I read there, there is very little chance that it is genetic, or hereditary. It seems that one of the main characteristics here is a severe allergic reaction to medications, and drugs, as well as things like cat-scratch fever, and herpes simplexes. I am not a doctor, but what I read there, implies that it isn't hereditary. Go and read about it please. Hope this helps, good luck.
Both my son and I have each had several episodes of Stevens Johnsons Syndrome, some of which were very serious, so that would seem to suggest that it is hereditary, or - at least - that there is a genetic predisposition to developing the condition. Almost all our reactions were to prescription medicines, though, rather than to foods or environmental allergens - and we both reacted to a particular form of Penicillin.
Of course, it may just be that a tendency to allergies runs in families, but that not every family member will be allergic to the same things. My daughter gets terrible hay fever, but has so far never shown any signs of any more serious allergies, thank God - despite having had Penicillin on numerous occasions. (My son and I have to stay well out of the way when she takes it, though!)
I also had a very severe case of Steven Johnsons Syndrome when I was 20. I was hospitalized for a week, couldn't eat or drink for 3 weeks anything except water. SJS is very serious, and unfortunately still very unknown. I have two young children now and it's frustrating that Dr's often overlook the severity of SJS. Most importantly it's not often understood that the real danger that SJS causes is due to it's delay in even reacting. Unfortunately I still do not have an answer as to whether or not it's hereditary. I'm going to be as cautious as possible with my kids exposure to antibiotics, but I too would love to know for sure how great a threat there is of them getting the same allergy.
