Hidden mold is on most homeowners’ list of basic nightmares. You can’t see it, but you may be able to smell it — and if you have allergies or asthma, your body knows it’s there for sure and may sneeze, wheeze and cough in protest.

Related: Ban These 7 Allergens from Your Home

So how can you find it, and more important, get rid of it and make sure it doesn’t come back?

First, a few words about mold. It’s a fungus that grows best in warm, damp and humid locations. It can survive indoors and outdoors at any time of year. Mold spreads by producing tiny spores that are released into the air. If these spores land on a damp spot, they’ll start to grow.

If you’re allergic to mold, it can set off your allergies or asthma if you breathe in the spores or touch the mold directly. In addition to sneezing, coughing and wheezing, mold allergy symptoms include a runny nose, itchy eyes and trouble breathing according to the Asthma and Allergy Foundation of America.

Mold is not toxic or poisonous, but certain types can produce toxins that may cause health problems, For example, Stachybotrys atra, aka black mold, produces toxins that may trigger pulmonary hemosiderosis, a condition that causes bleeding in infants’ lungs, though a cause-and-effect connection has not been proven according to the Centers for Disease Control and Prevention (CDC). This uncommon mold appears as a greenish-black fungus on materials with a high cellulose content that have been chronically exposed to moisture, like drywall, dropped ceiling tiles and wood.

Related: Clearing the Air: 3 Dangerous Pollutants in Your Home

Where mold grows

Mold thrives in moist areas such as:

  • around windows where moisture condenses
  • near leaky sinks or pipes
  • on basement walls or in a crawlspace
  • on bathroom tile
  • in or near shower and tub areas
  • on exposed insulation facing in attics
  • in washing machines
  • on the refrigerator’s gasket or water dispenser drip pan

Not all molds grow in places you can see. Some hide in places you might never suspect. According to the Environmental Protection Agency (EPA), the top places mold hides include:

  • the backside of drywall
  • behind wallpaper or paneling
  • on the top side of ceiling tiles
  • underneath carpets and pads
  • inside walls around pipes or on wood framing (due to leaking or condensing pipes)
  • the surface of walls behind furniture (where condensation might form)
  • inside ductwork
  • in roof materials above the ceiling (due to roof leaks or insufficient insulation) 

Related: 6 Cleaning Mistakes You’re Probably Making

How to recognize a mold problem

Sight: Conduct a visual inspection, the CDC advises. Mold can appear as a gray, white, brown, yellow, green or black discoloration on a surface.

Smell: Mold gives off a distinct smell. No doubt you’ve walked into a basement and detected a musty or earthy odor. This is a clue mold may be present.

Testing: Only a test can determine the exact type of mold you have, so if you’re concerned about black mold, have a mold sample tested. Hire a mold removal specialist or contractor to do this.

How to get rid of mold

If you have mold, don’t delay cleaning it up. The quicker it’s removed, the less chance it has to spread and cause further damage, the EPA advises. If mold growth exceeds 10 square feet, the EPA suggests you consult this guide to getting rid of mold in commercial areas.

Start by bringing the moisture under control. Fix plumbing, roof or basement leaks or any other water problems and dry the affected areas completely. Then scrub mold off hard surfaces with a simple detergent and water. You can use a commercial product or a bleach solution of no more than 1 cup of bleach in 1 gallon of water. Do not mix bleach with ammonia or other cleaning products as this may produce toxic fumes. Wear non-porous gloves and protective eyewear, and ventilate the area by opening doors and windows. The EPA suggests buying a N95 respirator mask from a local hardware store to limit exposure to airborne mold spores.

If you don’t want to clean the mold yourself or you have a mold allergy that would make the job hazardous, hire a contractor or a mold removal specialist.

If the mold is in places you can’t get to, like behind wallpaper or inside walls, you’ll probably want to hire a professional, since tearing off wallpaper or drywall can make things worse and lead to the rapid release of mold spores.

Tips to prevent mold

To keep mold from flourishing in the first place, follow these suggestions from the EPA and CDC:

  • Clean up water leaks, spills and condensation promptly. Mold will generally not grow if the wet or damp area is cleaned within 24 to 48 hours.
  • Routinely clean gutters.
  • Grade exterior dirt so it slopes away from your home’s foundation.
  • Regularly clean air conditioning drip pans and drain lines.
  • Measure the indoor humidity with a humidity meter. Keep levels between 30 and 50 percent by running a dehumidifier if needed.
  • Keep kitchens and bathrooms well ventilated by opening windows or turning on exhaust fans when cooking or showering.
  • Use mold-killing cleaning products in the bathroom.
  • Do not carpet areas where moisture is likely, such as bathrooms and basements.
  • Use a mold-inhibiting paint in areas susceptible to mold." (A mold-inhibiting paint is specially designed for high moisture areas. The paint packaging will say "mold and mildew-proof paint.")

You can’t completely eliminate mold and mold spores from your home, but by taking these steps you’ll get mold under control and help anyone under your roof who has allergies breathe easier.

Related: Tips for Greener House Cleaning

Brian Fourman is a stay-at-home dad who writes about home safety and personal finance.