The origin of sushi is believed to have been during the second century A.D. in Southeast Asia. It developed through a need to keep meat fresh without refrigeration. Meat and fish would be cured and wrapped in rice to preserve its freshness. The idea eventually spread through China and then to Japan, where fish is a food staple. The Japanese would ferment their cured fish and rice sushi with Japanese rice wine, or sake.
A lot of sushi is naturally dairy and gluten free, just be careful of any wheat based soy sauce.