Mold and Allergies

By: Karen Serrano, MD

Molds can cause allergy symptoms throughout the year. They can be present indoors or outdoors. They exist anywhere there is moisture, oxygen, and other elements they need to grow.

Outdoor molds can be found almost everywhere, especially in areas where there is soil, vegetation, or rotting wood. Shady, moist areas with fallen leaves are excellent places for mold. There are also mold seasons. Outdoor mold spores appear after the so-called spring thaw or when the weather starts to get warm. In warmer areas, they peak in mid-summer. In cooler areas, mold counts don't peak until October. Check with your local Health Department for more information about peak mold seasons in your area.


Indoor molds, however, occur year-round and are found in damp and dark areas, including:

  • air conditioners
  • attics
  • barns or stables
  • basements
  • bathrooms
  • carpets
  • crawl spaces
  • garages
  • garbage containers
  • greenhouses
  • houseplants
  • mattresses
  • old foam rubber pillows
  • places with standing water
  • pool houses
  • refrigerators
  • summer cabins that have been closed up
  • under sinks
  • upholstery

Tips for Reducing Mold to Limit Allergies

While you can't entirely escape mold spores, take these steps to decrease the amount of mold in your home and office and reduce allergic reactions to molds.

In the Yard

  • Avoid outdoor places where mold is likely to be in high concentration. These include shady areas, compost piles, kennels, and piles of leaves, grass, or straw.
  • Promptly repair and seal leaky pipes and roofs.
  • Have the yard mowed and raked regularly. If possible, have someone else do it.
  • Keep rain gutters clean. Clear leaves and debris from drainage areas around your home and yard.
  • Store firewood away from the house.

House Cleaning

  • Cleaning your house regularly and properly can help reduce mold.
  • Dust-proof your environment. Since mold spores can become part of house dust, follow the strategies outlined in Dust Mites and Allergies.
  • Clean with a commercial antimold product. Choose a product containing a mixture of bleach and detergent or make your own antimold cleaner. Mix 1 tablespoon chlorine bleach and 1 quart of water.
  • Clean carefully, especially in areas where mold is likely to grow, such as bathrooms, kitchens, and basements.
  • Empty refrigerator drip pans and thoroughly clean them with a commercial antimold product.
  • Keep garbage cans and trash compactors clean and free of mildew.
  • Store things carefully. Don't store newspaper, clothes, and other items in damp areas because they can become moldy. Store only completely clean and dry clothing and shoes. Even small amounts of grime can stimulate mold growth.
  • Throw away any moldy foods lurking in your refrigerator and cupboards.

Dehumidifiers and Fans

  • Use a fan in the bathroom to remove damp air. If you don't have a fan, open a window and consider having a fan installed. In bathrooms without windows, open a door when you're finished, and consider using a dehumidifier.
  • Use a dehumidifier to dry out a damp basement, but be sure to empty the water from it and clean it regularly. Water left in dehumidifiers allows mold to grow.
  • Don't use humidifiers or vaporizers. Putting extra moisture into the air encourages mold growth. If you choose to use these appliances, follow the manufacturer's instructions about regular cleaning. Even special humidifiers designed to lessen mold growth require regular and thorough cleaning.
  • Ventilate closed rooms by opening doors and installing fans.

Sleeping, Decorating and Lighting

  • Avoid sleeping in areas of the house that are below ground level.
  • Don't put carpeting directly on concrete or damp floors. The carpet may become moldy.
  • When painting damp areas, choose mold-inhibiting paints. They can be found at most paint stores.
  • Have someone remove all carpets and wallpaper with visible mold or mildew.
  • Don't overwater plants. A few household plants probably will not cause allergy symptoms if you're mold-sensitive. But standing water promotes mold growth.
  • Keep windows sealed tightly. You may need to replace weather stripping on older windows.
  • Eliminate dark areas. Most mold needs darkness to grow. In the basement or in closets that tend to be damp, install a light on a timer. Add windows or skylights to dark rooms.


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Written by Karen Serrano, MD Emergency Medicine resident at the University of Wisconsin-Madison.

Reviewed by Lisa V. Suffian, MD

Instructor of Clinical Pediatrics in the Division of Allergy and Pulmonary Medicine at Saint Louis Children's Hospital, Washington University School of Medicine

Assistant Clinical Professor in the Department of Pediatrics at Cardinal Glennon Children's Hospital, Saint Louis University

Board certified in Allergy and Immunology

Last updated June 2008