Is Dirty Sock Syndrome Dangerous? What is It and How Do I Fix It?

Is Dirty Sock Syndrome Dangerous? What is It and How Do I Fix It?


Those of you who read our articles regularly, know that we are a small, U.S. Veteran-Owned company in Southern California, and pride ourselves in giving people honest, straight answers to their questions.  This will be no different.  So, what is dirty sock syndrome?  “Dirty Sock Syndrome” is when your air conditioner gives off a foul, moldy or mildew-like smell when you turn it on.  If you notice that your house smells like your son just put his gym socks into your air conditioner or if your house generally smells musky or like a gymnasium when your air conditioner kicks on, then you could have dirty sock syndrome.  I think it is important for me to point out at this point that no, I am not joking.  This is a real problem that people face and it is actually called ‘Dirty Sock Syndrome’ in the HVAC industry.  In Santa Clarita, we get questions about this from time-to-time, usually in the springtime when people are transitioning their HVAC units from heating to cooling mode.  So, what causes dirty sock syndrome, and is it dangerous to me or my family?  In this article we will briefly explain what it is, what causes it, if dirty sock syndrome is dangerous, and what you can do to fix it.

dirty sock syndrome dangerousWhat Is Dirty Sock Syndrome and What Causes It?

Dirty sock syndrome is the foul, moldy smelling odor that comes from your air conditioner when you first turn it on.  It is caused by the build up of mold and bacteria on your evaporator coil.  Mold and mildew can grow due to the moisture that builds up on your coil through continued use, is fueled by the dust that collects in your air conditioner over time from inadequate filtration and is especially common when your unit goes from a period of heating to cooling.  Especially in the Springtime in Southern California and the southern states, it is not uncommon for the heat to be on in the night and morning, only to transition to a period of cooling later in the day.  This heat mixed with dust and moisture in the darkness of your AC unit is the perfect recipe for dirty sock syndrome.  These are some of the reasons that it is so important to prevent mold and to provide adequate filtration for the air entering your air conditioner.  In fact, did you know that the air conditioning filter that you replace every few months is actually for your air conditioner, not for you?  Here are a couple of articles on preventing mold in your AC unit and how to properly choose your air conditioning filter:

dirty sock syndrome dangerous - moldy coilDo I Have Dirty Sock Syndrome?

Before going to general quarters, it is important to rule out some other possibilities before jumping to the conclusion that you have dirty sock syndrome.  Here are a few things to rule out before calling your local HVAC contractor:

  • Make sure that your drainage pans are empty – if they are full, empty them and clear any blockages.
  • Ensure that your air conditioning filter is providing proper filtration for your air conditioner, and is not moist.  If it is wet, replace it.
  • Clear any drainage lines that may be blocked.  Some moisture in your air conditioner is common, but excessive moisture is a problem.

If you have done these things and are still suffering from moldy, noxious smells when your air conditioner kicks on, then it might be time to call your local HVAC contractor.  For information on choosing the right contractor, make sure you take a look at:

dirty sock syndrome dangerous - cdcIs Dirty Sock Syndrome Dangerous?

The short answer is, it depends.  

Usually the answer is no, dirty sock syndrome is not dangerous.  Dirty sock syndrome is caused by a variety of bacteria and mildews, none of which are harmful to your health under normal circumstances (normal immune system, etc).  Where you can get into a dangerous area is if mold gets introduced into your HVAC system and begins to grow.

Mold can be a health risk to you and your family and should be handled appropriately.  Don’t go crazy just yet though – as a general rule, the CDC reports that most molds are only mildly toxic to humans and that symptoms in even heavily infested homes rarely progress past chronic coughing and wheezing.  This is obviously not desirable though, so mold should be reported to your landlord or properly handled as soon as possible.  After I just got your blood pressure up, it is important to keep in mind that just because you have dirty sock syndrome doesn’t mean that you have mold, so don’t go off the deep end; just open up your system and see what you’re dealing with.

But if you’re curious, you can see how much a new air conditioner would run you:

Where we start to run into problems with dirty sock syndrome is if someone in your family suffers from asthma, severe allergies or has a compromised immune system (chemotherapy, etc).  For instance, my wife suffers from moderate asthma and we take mold and allergens very seriously because we have to, using only high-quality air filters and I even clean our evaporator coil once every few months (I’ll show you how to do this in the next section).  We’ve added a stand-alone air purifier to our bedroom and a UV air purifier to the air conditioner as well just to be safe and it works pretty well for us.

You have customizable options – your household might be different, so it is worth a little looking into (if you have questions, just give us a call and ask).  Dirty sock syndrome doesn’t automatically mean that you have mold, but it does mean that your AC unit is providing the right conditions for mold to grow and thrive, so keep an eye on it.  We will address how to deal with it in the next section.

Dirty sock syndrome isn’t usually dangerous and it isn’t going to kill you, but you should still address it if it becomes a problem to say nothing of the fact that it just plain stinks!  For more information on mold and possible side affects of living with mold, take a look at the CDC:

If you have a loved one who suffers from severe allergies or from asthma, try reading up on this:

How to Prevent and How to Treat Dirty Sock Syndrome

How to Prevent Dirty Sock Syndrome:

The most important factor in preventing dirty sock syndrome is to make sure that you choose a high-quality air conditioning filter.  Mold, mildew and bacteria need dust and other porous substances to thrive.  Removing these from the air before they get into your coils is one of the key ways to prevent dirty sock syndrome.

The second way to prevent mold and bacteria from growing on your cooling coils (called evaporator could) is to use a UV air purifier.  These air purifiers have been used in hospitals for decades and quickly kill bacteria, mold and it’s spores.  At All Systems Mechanical, we install a UV air purifier on any job where our client reports allergy, asthma problems or a compromised immune system, so it might be worth asking your HVAC contractor if you have a problem with these as well.  There are several companies on the market that make UV air purifiers, but I have always been a fan of Honeywell.  They make quality products and are reliable.  Here is some more info:

Honeywell UV Air Purifiers.

How to Treat Dirty Sock Syndrome:

I have some bad news: you can definitely remedy the situation by cleaning your coils, but thats not a guarantee.

  • The only way to 100% eliminate dirty sock syndrome and the odors associated with it, is to replace your evaporative coil.  Often times, depending on the age of your air conditioner, it may just be a good idea to replace your whole air conditioner.

But first, let’s try to clean it and see if that helps!

Start by checking your drainage pan for standing water and make sure it is draining properly.  You can buy dissolvable tablets at a hardware store or online that will keep these drains clear.  After ruling out the drainage pan and other possible contributing factors, you should start by adding the preventative measures listed above (quality air filter and UV air purifier) as these are key to keeping it from coming back (what’s the point of cleaning it if it is just going to be back in a few months).  Then, you’ll have to clean your evaporator coil to get rid of the dirt, mold and bacteria that is already there – here’s how:

How to Clean Your Evaporator Coil:dirty sock syndrome dangerous - how to clean evaporator coil

  1. Always start any maintenance or cleaning of your air conditioner by turning off your AC unit at the thermostat and then by also turning the HVAC circuit breaker off on your main power distribution panel (aka your circuit breaker panel).
  2. Make a solution of one part bleach to three parts water and place it in a bucket with a scrub brush.  An old scrub brush is ok to use, but plan on throwing it away when you are done with it!  If the odor is really bad, then I’d spend the money and buy some VindEx.  VindEx is a special solution that is clinically prevent to destroy the bacteria and mold known to cause dirty sock syndrome.  More information can be found here: VindEx – The Cure for Dirty Sock Syndrome.dirty sock syndrome dangerous cleaning solution VindEX
  3. Next, I’d get a pair of safety goggles and put them on – you don’t want any of this stuff getting in your eyes, neither the bleach nor the stuff you are about to kill with bleach.
  4. Locate the evaporator coil inside your HVAC unit.  You will have to open a panel on the outside of your unit.  This will take a little time to figure out based on your unit and every unit is different, but be patient.  It will look something like the picture above by step 1.  If you have a split-unit (meaning two different parts to your air conditioner, one outside and one inside), the evaporator coil will be inside the indoor part of your air conditioner.
  5. If there is a lot of dust and debris, start with a vacuum and remove as much of this as you can (use a shop vacuum if you have it).
  6. Finally, scrub your coil thoroughly using a motion that goes in the same direction as your coils.  Clean the coils and surrounding areas throughly, making multiple passes.  Finish by drying the entire area with an old (disposable) towel or paper towels.  If you have a wet-dry or shop vacuum, take one more pass to remove as much moisture as you can (this step is optional).
  7. Discard water, brush and all towels, then wash your hands thoroughly.

Save Money on Your New Air Conditioner by Watching This Short Video

Look…in some cases you can get rid of dirty sock syndrome, but if you still can’t get rid of the smells, then you may have to think about replacement.  Before you do anything, make sure that you educate yourself on how much this might cost.  This short video will show you how we can help save you money, and avoid the tricks and traps of predatory contractors:


Final Thoughts on Dirty Sock Syndrome

Is dirty sock syndrome dangerous?  Not usually, but it can be annoying and downright embarrassing.  After all, who wants their house to smell like a locker room?  These smells and odors are a direct result of the mold and bacteria that can collect in your air conditioner, but there are several ways to prevent and treat them.  If something your contractor is telling you doesn’t seem quite right, or you need a second opinion, consider using our Online Air Conditioning Consultation Service.  For more information of related topics, visit ASM’s Air Conditioning Blog.  If you live in Los Angeles or the Santa Clarita area, feel free to give us a call at All Systems Mechanical HVAC, we’d be happy to help you in any way that we can.


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Timothy Kautz
About the author
Tim K.

The University of Virginia - 2005 / The Wharton School of Finance - 2016 / U.S. Naval Aviator 2005-2015. At All Systems Mechanical air conditioning and heating, we believe that the experience our clients have is every bit as important as the products they receive. Simply put, our results speak for themselves, and we'd be happy to help. If you're in the market for a new AC or furnace, make sure that you get a fair price! Try our online calculator; click the tab on the top of this page for more information.

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