I will occasionally notice minor molds developing on bread I've left for a few days at room temperature. Often, there will be some mold noticeable on a few pieces, while other pieces are fine.

I know next to nothing about molds in general. Aside from the "ick" factor, is consuming a piece of bread with a small amount of mold on it dangerous? What adverse health effects (if any) could result?

2 Answers 2


There are a couple concerns with eating food with mold on it:

  1. The growth of mold implies that microbial contaminants can grow on the food, which means there is a potential for spoilage even if the mold itself isn't pathogenic.
  2. The mold itself can cause health problems. The USDA recommends discarding molded bread, as a "bit of mold" that is visible likely means a much greater penetration of mold in sub-visible amounts throughout the bread as a whole.

The most common health threats from the mold itself are likely exposure to mycotoxins or allergic reactions - consider, for example, that penicillin is a mold that can grow on bread, and also causes fairly serious allergic reactions.

While the risk is likely small (you are exposed to tremendous numbers of molds in the process of going about your life), it's also fairly avoidable.


Molds, fungus and yeasts produce mycotoxin, a toxic chemical which can cause both acute and chronic health effects via ingestion, skin contact or inhalation2012. The danger associated with exposure depends on the type of mycotoxin, concentration and length of exposure as well as exposed individual (age, health and sex)2003. In same rare cases can be even deadly (aflatoxins)2005.

In comparison, molds such as found on blue cheese are harmless, because they contain specially cultivated bacteria and they're considered safe to eat.

Therefore if you're not sure what kind of mold it is, for your own health your should limit your exposure to all kinds of molds, fungus and yeasts.

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