Why is Blue Cheese Blue?

Cecil's Columns/Staff Reports
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SD staff member Una wrote:

“The name Penicillium roqueforti sounds like penicillin because it’s related to the common and useful antibiotic mold. This relation is more than just skin-deep, as blue ripened cheeses do seem to inhibit the growth of harmful (and other) bacteria, such as Clostridium and Staphylococcus. However, lest you think that eating lots of Roquefort will clear up that nasty infection, know that most cheeses contain relatively small levels of antibiotic mold relative to that found in concentrated pharmaceuticals.”
http://www.straightdope.com/mailbag/mbluecheese.html

There’s not enough penicillin in blue cheese to kill an infection - very well. But is there enough penicillin to trigger an allergic reaction in someone allergic to the drug? Typical symptoms of such a reaction are swelling and joint pain.

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Penicillin allergy and cheese (“the conclusion of most of the material I’ve seen on this is that small amounts of penicillin in food seldom causes an anaphylactic reaction in penicillin-sensitive individuals.”)

But see, http://www.nlm.nih.gov/medlineplus/ency/article/000814.htm (“For example, a person who is allergic to molds may be allergic to penicillin and also to blue cheese, used in certain salad dressings.”)