Cheese which is intentionally blue, such as Stilton, have added blue mould spores within the body of the cheese. These moulds help to break the cheese down, and in the process they give it a stronger flavour and distinctive appearance. Sometimes other cheeses unintentionally develop blue mould. Air can penetrate the cheese through the rind of clothbound and natural-rind cheese. If the cheese is bumped during turning or has natural crevasses within it, moulds can sometimes grow inside them. Whether or not this is advantageous depends on the nature of the mould growth. Brown or grey moulds, or a ‘bruised’ appearance within the paste, are unattractive and not good to eat; on the other hand a streak of bright blue through a Cheddar or Cheshire adds complexity and was once a prized addition to the cheese (known as ‘Vinny Cheddar’ or ‘Green Fade’).  There is no danger in eating blue which has developed in this way, just as there is no danger in eating blue cheese. We encourage our customers to taste the cheese and see what appeals to them, but if you’re in any doubt, please send us a picture — if something has slipped through the net that is not up to standard, we’ll be happy to replace it for you.