Here is a link to IBS http://www.lactose.co.uk/ibs/
I suffer with this from time to time and found that if I lay off dairy foods it eases. Milk is the trigger for me.Don't know about the kelp though . I take thyroxine every day for thyroid and this is the same thing really ..iodine... and it hasn't had an adverse effect on the IBS.
Do see your GP though if you are worried .Good luck.