Take a look at the ingredients that are in your cheese. Many commercial Shredded cheeses have an antifungal agent called Natamysin. It is the Active ingredient in Natamycin Ophthalmic (Natacyn) a medication used to treat fungal infections of the eyes.
I don't know about you, but I wouldn't want to be consuming an antifungal agent.
So far I have only seen it in shredded cheeses. Read labels carefully. Buy from companies that do not use antifungal agents. Shred your own cheese to avoid this problem.