Skunky Beer: How it happens and How to avoid letting it happen

Posted on June 29th, 2009

Regardless of what your favorite type of beer is, the last thing any of us want to happen is to see a sixpack of our ale or lager of choice to go bad and get spoiled or “skunked.”

Although the term is frequently used to describe beer that’s gone bad for any variety of reasons, to be precise “skunked beer” refers to beer that’s been over-exposed to sunlight, or “light-struck.” What exactly does that mean, and how can you avoid this happening to your beer? Read on to find out.


Although there are plenty of ways to ruin a beer, overexposure to light is the only way to skunk it. Storing beer at room temperature won’t do it; re-chilling cold beer that’s warmed up won’t do it either.  These are common misconceptions, but the fact remains the only way to skunk a beer is to overexpose it to light.

The reasons why light is so damaging to your beer gets technical fast, but basically, the light causes alpha-acids (the key component of hops) to break down and combine with other chemicals in beer to create 3-methyl-2-butene-1-thiol, a sulfur-containing substance which produces the strong sulfur smell which is extremely similar to isopentyl mercaptan, or skunk spray.  It’s easy to see why light-struck beer got its skunky nickname; it’s almost the exact same smell.

This is why most beer is sold in brown bottles or cans; the dark glass and opaque aluminum protect beer from most of the harmful UV rays that damage it, a good thing because beer without any protection can become skunked after just a few hours of exposure to direct sunlight. You shouldn’t worry about a glass of your favorite beer going skunky the next time you enjoy it on your patio, but give it an afternoon undisturbed and it might.

At this point you might be wondering about Newcastle or Miller High Life or another beer that comes in a clear bottle,  then of course there are also some European beers like Beck’s that come in green bottles. How come every single one of those beers doesn’t get skunked? Because those beers don’t actually use hops, they use a hop substitute known as tetra-hop, which thanks to the miracle of modern science avoids smelling like skunks when it’s exposed to sunlight. The downside of tetra-hops is it doesn’t smell like hops much at all either; it has almost no scent at all.

For the curious it’s easy to create skunky beer at home, just put a glass of your favorite beer on the windowsill for an afternoon and see how the smell compares before and after.  You can watch the guys over at Basic Brewing try this experiment themselves if you’re curious but still don’t want to waste a perfectly good beer in the name of science.

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  • lighthouse11

    What of us who happen to like the aroma of “skunky” beer? To me, it's a must just like fine skunk “buds” from Mendocino California. If I don't smell the skunk in my beer, it ain't worth drinking!

  • Joysemler

    There is a way to drink beer in a clear or green bottle and not have it skunk the second it hits lights.  SPF 2000 is a clear glass coating that blocks up to 99% UV rays. is the website I found.  Does anyone know more about this and how I can find bottles that use this stuff??

  • Rakempe

    Here’s a great video I found on You Tube about skunked beer 

  • BallantineFan

    Absolutely agree. I will purposefully place my green bottled beers in direct sunlight for a few days before chilling them.

  • sonnygreen

    “Skunked” beer is still OK to drink. After the first sip you won’t notice the difference.

  • Olan Suddeth

    For the record… I have yet to try a Newcastle that wasn’t skunked to the point of complete nondrikability. 

  • DaveMc

    Haha! I’m glad I’m not the only one who does this

  • Skunky McSkunkerson

    Funny I found this article after opening a very skunky New Caste brown ale.I bought it at a Utah state liquor store for double the normal price (the only place you can buy non-watered-down beer in Utah). I hate Utah. Their pizza is terrible too.

  • Susan Handsom

    Me too! I’m just now understanding how this happens. I thought I was the only one who likes this. Now I understand the puzzled look I got from a bartender when I asked for a bitter skunky beer! Saint Pauli Girl (in green bottles) is usually skunky, that’s why I buy it. Now I have the power to skunk! Huzza!

  • Tom O’Donnell

    I Have had 6 / 30 packs skunk Miller High Life, Now first 24 pack of skunk Miller light. All cans, no see through bottle excuse.

  • Tom O’Donnell

    Looks better all glazed too!

  • Jeff Keil

    only time I have ever had beer take on a skunky taste, was when it was left in a cooler outside during the summer for about a month. it was in cans and inside a closed cooler, so it definitely was not exposed to light. I would say prolonged exposure to moderately high temps can also ruin beer. it was Budweiser by the way so its not like it was some beer that I was unfamiliar with and just didn’t know what it was supposed to taste like.