Dirty Sock Syndrome (How To Easily Fix This In Your AC)

What is dirty sock syndrome? Is that terrible smell of wet gym socks coming from your HVAC system?

If you are experiencing this putrid, perturbing predicament and want to know how to fix dirty sock syndrome, what causes it, and if it’s dangerous, then read on through this helpful guide.

What Exactly Is the Dirty Sock Syndrome?

Dirty sock syndrome, or stinky sock syndrome if you prefer the alliteration, is the unpleasant smell that can sometimes creep out of your HVAC system. It is so named for its similarity to the smell of dirty socks.

In reality, AC dirty sock syndrome results from the presence of bacteria and fungus. The resulting smell is mildew.

Zoomed-In Mold Growing

Main Causes of Dirty Sock Syndrome

The causes behind the HVAC dirty sock syndrome are moisture and bacteria. If your house is too humid, moisture can collect in the HVAC system. When dust and dirt get sucked up into the system, as well, then the wet environment creates the perfect habitat for bacterial growth.

You will most likely find dirty sock syndrome in HVAC coils and the air filter, as this is where most dirt collects. It is also the spot where the air inside your house gets filtered out to make way for the incoming hot or cold air, which means any dirt from people, pets, bugs, or food may be sucked in.

If enough bacteria build up around the air filter and evaporator coils and the air is humid, then mildew will start to grow. Eventually, the mildew will accumulate enough that its smell gets dispersed throughout the house by the ventilation system.

Is Dirty Sock Syndrome Dangerous?

The good news is that dirty sock syndrome is not inherently dangerous. Mildew is a type of fungus that does not produce toxins, so while it is pungent and unsightly, it is unlikely to cause any health problems.

That said, it can exacerbate existing health issues such as allergies, asthma, and already compromised immune systems. Young children and the elderly are also at a higher risk of adverse health effects from dirty sock syndrome.

The longer mildew is left to accumulate, the more likely it is that people will start experiencing ill effects. Symptoms can range from discomfort breathing to allergy-like symptoms to cold and flu-like symptoms.

While mildew is a type of mold, it does not pose the same risks as other forms of mold, and even the infamous black mold is not as harmful as most people think.

To learn more about molds, follow this link to EPA’s page.

How to Get Rid of Dirty Sock Syndrome in Your House?

If you are tired of smelling dirty socks and want to know how to get rid of dirty sock syndrome in AC or HVAC systems, then follow these steps.

You may decide to call a technician or try to fix the problem yourself. In either case, you will need to clean or replace both the filter and evaporator coils.

Dirty sock syndrome in a new unit? Dirty sock syndrome in window AC? Same deal.

Make sure to wear a respirator when cleaning mildew. Brushes and compressed air are essential tools for cleaning the evaporator coil. Make sure to vacuum the area after, as well, and ventilate the house if you can.

If the evaporator coils and filter are too dirty, you may be better off replacing them. A technician can tell what “too dirty” is.

rheem air conditioner

Preventing the Dirty Sock Syndrome

There are a few tricks you can try that will help prevent the return of dirty sock syndrome once you have gotten rid of it.

Proper maintenance is the first step. Change the air filter every 60-90 days and call-in services whenever you feel the need. Duct cleaning, duck sealing, and a UV light installation will also reduce the risk of dirty sock syndrome.

If you need to replace the coils anyway, why not get one with epoxy coating to help prevent dirt from sticking. You can also take measures to reduce the humidity in your house, especially around the drainage point.

DSS in My Car: How Can I Remove It?

Dirty sock syndrome in cars is mainly due to condensation build-up. When you run the AC in your car, condensation can collect in the AC housing. When you turn the car off, and the water is left to sit in the heat, it can lead to fungal growth.

The next time you run the AC, you may notice the dirty sock smell. The mildew growing in the car AC is blown at you each time you run the AC.

The easiest and most effective solution to get rid of dirty sock syndrome from your car is to take it in for service. Auto shops are the best place to get the AC cleaned out and take measures to prevent it from happening again.

Vehicle Car AC Ventilation

People Also Ask (FAQ)

Does UV light help with dirty sock syndrome?

UV light is an effective way to kill microorganisms at a molecular level. In the same way that excessive exposure to sunlight can damage skin cells and cause cancer, it can also eradicate certain microorganisms.

The introduction of UV radiation to fungus-causing bacterial microbes can help remove the dirty sock smell from AC coils and drain pans.

Is dirty sock syndrome covered by warranty?

In most cases, the warranty will not cover dirty sock syndrome. Warranties are meant to cover malfunctions and manufacturer mistakes, not environmental conditions.

As dirty sock syndrome is not due to issues with the parts, most warranties won’t cover it. Some warranties, however, will at least partly cover the cost of replacing the evaporator coil if it has been damaged.

Will dirty sock syndrome go away on its own?

Dirty sock syndrome does not go away. You may not smell it as much or at all once you stop running the system. However, as it is caused by fungal growth, the problem does not simply go away.

The root of the problem must be removed and all affected parts cleaned. You will also have to take on preventative measures to reduce the risk of the smell returning.

How long does dirty sock syndrome usually last?

Dirty sock syndrome will last as long as you let it. Unfortunately, the longer you let the problem continue, the worse it will get and the harder it will be to get rid of it.


Dirty sock syndrome is nothing more and nothing less than the smell of mildew blowing through your vents. Cleaning the air filter and HVAC evaporator coils will eliminate the odor, but keeping your system clean and reducing the house’s humidity will prevent the issue from returning.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.