There are quite a few health food shops sprouting up in and around Dublin which, between them, stock a large variety of food allergy free products. This linked to the recent surge of food allergy awareness and likewise the development of more and more food-allergy friendly products makes shopping in Dublin with food allergies a much easier (and more pleasant!) task.
As much as I would love to list out my favourite shops, the cheapest shops or the most expensive I fear that it would not be a reliable list. The cheapest health food shop in vitamin and mineral supplements could be the most expensive in homeopathic remedies, The shop which stocks the most grain substitutes might have the worst selection of ready made breads and the shop with the widest variety of sweets and snack bars could easily be the shop with the smallest variety of pasta and milk substitutes. And of course location is a completely different kettle of fish! Instead I venture to give a 'free from bias' general review of the attributes of each location. This will hopefully lead you towards educated trips to the healthfood shop which best suits your personal requirements.