match cell text as input, text as output

I need help!!!

I am trying to find the right formula to automatically fill in a cell if we need to perform a certain task.

The conditions are: we make food, some recipies have allergens and if we go from an allergen to a non allergen we must do a certain cleaning procedure.

If we change from Soya to Soya, no special clean required, if we change from egg to Soya, special clean required, if we change from Soya to Soya and Egg, no clean, but if we change from Soya and Egg to Soya, special clean.

this may be confusing, I am not sure how best to explain it. I can either put each allergen in a seperate column, or have all of them in one column.