I'd add no eggs (at least not egg whites), no cow's milk, and you might want to wait or limit quantities of 'highly allergenic' foods like strawberries. If you offer him stringy veggies like celery, green beans, etc. AFAIK it's recommended that you steam them until soft and remove the 'strings'. Other than that, I can't think of anything strictly off limits. At five months I'd still introduce things one at a time to check for reactions, and keep it to purees unless you see definite signs he's ready to handle finger foods and want to try BLW.