I was cleaning out my fridge and came across a milk carton (2%) that was bulging. I opened the cap and it released gas, and a horrible smell. I poured it down the drain and ventilated my apartment. How likely is it that I could have contracted a pathogen just by breathing?

  • 1
    If it were likely, biological weapons would be very easy to mass produce by terrorists. Commented Aug 14, 2018 at 16:53
  • I estimate the odds to be exactly .0000000000001%.
    – Carey Gregory
    Commented Aug 15, 2018 at 1:41

1 Answer 1


Extremely unlikely. This is simply unpleasant but not dangerous. The gas is mostly carbon dioxide released by bacteria in the milk fermenting the lactose sugar. Other products of the fermentation cause the foul smell.

Drinking the milk is another matter, as there will usually be bacterial overgrowth and a build up of lactic acid which will cause gastrointestinal symptoms such as vomiting and diarrhoea. In rare cases a person could become more seriously unwell.


Nonpasteurized Dairy Products, Disease Outbreaks, and State Laws—United States, 1993–2006 by authors affiliated to the US Centre for Disease Control.

Wikipedia article on milk pasteurisation

  • @CareyGregory would not having reference automatically earn a downvote, in spite of how sound the answer is?
    – Ooker
    Commented Aug 15, 2018 at 4:40
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    @CareyGregory I have edited the answer with a couple of sources. Could not find anything specific to inhaling or being near vapour from spoiled milk, so the sources relate more to the bacterial changes and risks in spoiled milk and drinking it.
    – Chris
    Commented Aug 15, 2018 at 6:02
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    @Ooker That's up to the people voting, but I don't automatically downvote for missing references. I usually post a comment reminding the poster to provide them.
    – Carey Gregory
    Commented Sep 7, 2018 at 23:20

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