Oh it absolutely affects the ratio of safe to contaminated food. The game was made in 7 days for a jam so I just made the chef choose from random dishes and random ingredients, but the presence of ingredients in dishes is not balanced at all. Oyster and crab barely ever appear but if you get an allergy like egg, you would be lucky to even reach 3 dishes lol.
That being said we are planning on changing that, and doing a general rebalance of the game so watch out for that.