You have provided the same information found on a million+ web sites. You have reiterated what clueless doctors have found: The cause is not known, no cure. Yet, they prescribe drugs for this? Treating something topically might be fine for a few hours but, topical applications are not addressing the source of the problem.
The source of the prob is most likely thin intestinal walls or compromised mucosal lining. Intestinal toxins are being released into the blood stream and coming out on your skin. Do things and eat (drink) things that will heal your insides.
Hereditary? Yes. Your intestines look like your father's intestines.