Why Is There a Strange Cheese Smell in My House?

By HomeSmitten Team · · Updated

Why Is There a Strange Cheese Smell in My House?

The quick answer

A cheesy smell is almost always bacteria or mold feeding on something damp: spoiled dairy or food, a fridge spill, a dirty drain or dishwasher, or buildup on the air conditioner coil. Check the fridge, trash and sink first, then the dishwasher, then your HVAC system. A cheese smell isn't a gas or carbon monoxide warning, but if the smell turns burnt, or reminds you of rotten eggs, switch to the safety steps below.

Cheese smells strange because it's a tell for something growing where it shouldn't. That's the stake: the smell itself is usually harmless, but it points to moisture, food waste or a dirty system that will keep smelling until you fix it. The food-safety side matters too, since spoiled food in a fridge or trash can be hiding in plain sight. For other smells and how urgent each is, see strange smells in the house.

Rule Out Danger First

This takes a minute. A pure cheese or sweaty-sock smell doesn't match the warning smells, but other smells get described as "off" or "sour," so check these:

  • Rotten egg or sulfur smell. Natural gas is odorless until a utility adds mercaptan, which Washington Gas says smells like sulfur or rotten eggs. If you smell that, leave and call your gas company or 911 from outside. Don't use switches or phones inside.
  • Burning or hot-plastic smell from an outlet, appliance or panel. Mr. Electric says burning smells come from overloaded circuits, melting insulation and failing outlets. Stop using the item, turn off power to the area if it's safe, and call a licensed electrician.
  • No smell, but headaches or dizziness in several people. The Consumer Product Safety Commission says carbon monoxide is colorless and odorless. Get outside and call 911.

If none of those fit, work through the everyday causes below, starting with the ones that take the least time.

The Fridge, Trash and Pantry

Dairy that has gone off gives a sharp, cheesy, sour smell, and so does a spill that has dried in a corner of the fridge. The FDA says to keep the fridge at or below 40°F, clean it regularly and wipe spills right away. Its rule for doubtful food: if you're not sure, throw it out. It also says you can't rely on appearance or odor to tell whether food is safe, so don't sniff-test food you're unsure about.

Check these spots in order (our judgment on the order):

  • Open milk, yogurt, cream, soft cheese and leftovers with dairy in them.
  • The door shelves, the crisper drawer and under the drawers, where drips collect.
  • The trash can and the lid. Empty the bin, then wash it with detergent and hot water.
  • The pantry and cupboards, for a cracked jar or a bag of something forgotten.
  • Pet bowls and pet food storage, which can smell sour when residue builds up.
What is this weird cheese smell in my house?

After you remove the source, wash the shelves and walls of the fridge with warm soapy water and dry them. A smell that returns within a day or two usually means you haven't found everything.

Drains and Sinks

Food residue builds up in a kitchen sink drain and garbage disposal, and bacteria feed on it. The result can smell sour or cheesy, especially when you run hot water. Pull out any visible gunk, flush the drain with hot water, and scrub the visible sides of the opening with a brush and dish soap. Check under the sink for a slow leak too. A damp cabinet floor is a good place for a smell to start (our judgment).

A dry drain is a different problem, but it's easy to confuse with this one. The South Davis Sewer District says the water in a drain trap can evaporate when a drain goes unused, and then sewer gas can enter the room. Its fix is to pour a cup or two of water into seldom-used drains, and run water in every sink, shower and floor drain at least once a month. If odors continue, the trap may be damaged, a vent may be blocked or there may be a leak, and a licensed plumber should look at it. Sewer gas contains hydrogen sulfide, which the CDC says smells like rotten eggs, so that smell would feel more like sulfur than cheese.

The Dishwasher

A dishwasher is a common hidden source of cheesy smells. Samsung's support page says mold or mildew grows where there's moisture, warmth and food particles, and that dirty dishes left inside between loads often cause a lingering smell. It also says the smell can come from the connected sink drain or garbage disposal, and that a large amount of water left after a cycle can mean the machine isn't draining.

Samsung's cleaning steps are:

  • Remove the racks and the filter, if your model has one.
  • Take the filter apart and clean each piece, then clean the drain area and filter housing with warm soapy water.
  • Check the spray nozzles for clogged holes and clear them with a thin, pointed object.
  • If the smell stays, clean the sink drain or garbage disposal. If it still remains, contact a plumber before cleaning the dishwasher again.

Filter location and cleaning steps differ by brand and model, so use your manual. The model number is on a label inside the door frame, and the maker's support site usually has the manual as a free download.

An Air Conditioner or Heat Pump

If the cheese smell shows up only when the air conditioner or heat pump runs, the evaporator coil may be the source. HVAC technicians call this "dirty sock syndrome." HVAC.com says it's typically caused by mold, mildew and bacteria growing inside the system, mostly on the evaporator coil and drain pan. Moisture from humidity condenses on the coil, and dust, poor airflow and skipped maintenance make growth worse. The smell is most noticeable when the system switches on for cooling, and it tends to show up in spring or fall.

HVAC.com's fixes include a professional coil cleaning (it says this typically isn't a do-it-yourself job), changing the filter every 1 to 3 months with a type that fits your system, a UV light in the system, and a dehumidifier or better ventilation. It also says the odor could point to mold, bacteria or a bigger air quality issue that can affect your family's health, so don't ignore it. Cheese isn't the exact word sources use for this smell. They say dirty socks. We're treating the two as the same family of smell, and that is our judgment.

Don't pour bleach or cleaner into the system yourself. If the smell is only there when the system runs, call an HVAC technician and tell them when it happens.

Damp and Mold

Mold can smell musty, sour or cheesy, depending on what it's growing on. The EPA says a moldy smell with no visible source can mean hidden mold behind drywall, wallpaper or paneling, or inside ductwork. It says to dry water-damaged areas and items within 24 to 48 hours, and to keep indoor humidity below 60 percent, ideally between 30 and 50 percent.

For cleanup, the EPA says homeowners can often handle areas under about 10 square feet. A professional is the better call for larger areas, sewage-contaminated water, suspected hidden mold or a contaminated HVAC system. If the HVAC system may be contaminated, the EPA says not to run it until you've checked. See a health professional first if anyone in the home has health concerns.

Look at the places where water collects: under sinks, around the washer, behind toilets, window sills with condensation, basements and the walls behind furniture pushed against an outside wall.

A Short Plan

  • Rule out gas, burning and carbon monoxide first.
  • Clear out the fridge and trash, and wash the bin.
  • Clean the sink drain and run water in unused drains.
  • Clean the dishwasher filter and drain area.
  • If the smell comes with the air conditioner, book an HVAC cleaning.
  • Dry any damp spots within 24 to 48 hours, and call a professional for large mold or sewage water.

Frequently Asked Questions

Why does my house smell like cheese?

The usual causes are spoiled food or a dried spill in the fridge or trash, a dirty drain or dishwasher, bacteria on the air conditioner coil, or mold in a damp spot. Check them in that order.

Is a cheese smell dangerous?

Not by itself. It isn't a gas or carbon monoxide warning. Mold and bacteria can still affect health, so find the source. If the smell is burnt or like rotten eggs, follow the gas and electrical safety steps instead.

Why does my air conditioner smell like cheese or dirty socks?

Mold, mildew and bacteria can grow on the evaporator coil and drain pan. The smell is usually strongest when the system first turns on. A professional coil cleaning is the typical fix.

How do I get rid of a cheese smell?

Remove the source. Throw out doubtful food, wash the fridge and trash can, clean the sink drain and dishwasher filter, and dry damp areas within 24 to 48 hours. If it only happens when the air conditioner runs, call an HVAC technician.

Sources