Thanks for writing in.
I would like to reassure you that ischemic colitis
is something which can be taken care of to a very large extent. However, the exact course can be determined by actually assessing the severity of the disease.
As far as your allergies are concerned, seafood and shellfish allergies are some of the most common ones. It is surprising you weren't diagnosed with this before. This can not only occur when you ingest sea food but can also occur when you inhale the protein when it is being cooked.
I would suggest you stay away from the seafood restaurant and you should be good.
Hope this helps.