I haven't been to either of these countries, but I have been to 3 others, and
brought in tinned food, and fruit for myself. I wasn't bothered if they were
taken from me though. But experienced no problems at all. Just pack whatever
you think in his suitcase, spreading it out so it doesn't look like he's
bringing lots of food in. He will probably find it a lot easier to be
dairyfree there as most foods are not processed at all. Much simplier eating.
Quite nice too. And surely your parents can watch out for him?

Hilda