I don't know, but there is definitely a minimum requirement. I tried it at level 15, and that was a mistake. I ran into a room with 2 Draugr Deathlords and a Draugr WIght. I don't think Deathlords even normally occur at level 15 in regular Skyrim. Needless to say, I went back to the mainland and did Dawnguard instead.
it depends i have an orc lvl 4 going in and im doing okay but my game is on easy cause dragons are brutle, anyway it depends on your skills and your play style, just remember your gonna die a LOT. Good luck
This is a old thread but like 18.104.22.168 said (and if the difficulty is set around the middle) between level twenty and thirty seems to be the generally recommended level (a fair fewcreatures on Solstheim start off around those levels), also as some else said it depends on how focused your skills are on combat.
It is probably better to wait until you can start the opening quest Dragonborn properly, and thats after a few of the main quests from Skyrim (and then the quest should come and find you).