Why There Are Holes in Swiss Cheese

Geobeats offers a yummy bite size explanation as to why there are holes in Swiss cheese. Rather than it being from the ripening bacteria or pesky little mice, the holes (eyes) were originally caused by hay particles that got into the open bucket mix. When machines came along, this hay particle was added to the milk.

Only certain kinds of Swiss cheese have eyes, and in the cheese industry, the rest are called blind.