Documents: Special Interest: Horticultural Therapy:

Soil Mold and Allergies/Asthma
by Jerry Filipski
by Jerry Filipski


Gerald (Jerry) Filipski is the gardening columnist for the Edmonton Journal, a position he has enjoyed as a freelance writer for the past 12 years. Jerry also writes for Canadian Gardening, the new Alberta Gardener as well as for the lifestyle magazine of P&O ferries. Jerry also does numerous public speaking engagements including some major gardening conferences and workshops as well as question and answer sessions for Wal-Mart and Rona.

July 27, 2008

Can soil molds on indoor plants cause health problems and how large a problem is it? There are a variety of molds that can live in and on soils of indoor plants.

These molds can be responsible for a number of health related problems ranging from mild to severe allergic reactions and can act as asthma triggers. The questions is how concerned should we be?

What are molds?
Mold, mildew, and fungi are all terms generally used to describe a group of diverse plants which appear as woolly or powdery growth. Molds are everywhere, indoors and out, in every type of climate, and in every social condition. They grow in places we would not expect. They are elusive and will be more prevalent at different times of the day or night depending on the type of mold. A single mold can germinate produce hundreds of thousands of airborne spores in 4-9 days.

Mold needs moisture, food, which can be any organic matter, and preferably warm temperatures. Relative humidity below 40% discourages mold growth. Molds are found in soil and in decaying leaves, straw, grains, and wood, for example.

Mowing the grass; raking leaves, working in the soil, or repotting an indoor plant can bring on symptoms associated with mold allergy.

Symptoms and sensitivity
As with most allergies sensitivity to the allergen is the key. This is very much an individual situation.

While some people may be sensitive to one specific mold, others may be sensitive to all molds. Which category a person falls in can only be determined by allergy testing.

There are generic symptoms that should prompt a visit to your physician for examination and testing. The number of symptoms that occur and the severity depends on how much mold is present, how long you are exposed, and how sensitive you are to mold. Some may experience only a few symptoms, while others will have all or most of the symptoms.

Often, mold allergy sufferers feel like they have a mild cold and take a cold medicine [most cold remedies will help a mold allergy reaction]. Most colds and flu are of short duration and usually much more severe than mold allergy reactions.

Symptoms can be:

  • Ear, Nose, and Throat- nasal congestion or sudden unblocking of congestion, nasal itching, runny nose, sneezing, hacking cough, ringing in the ears, earache dizziness, recurrent ear infections [especially in children], fluid in middle ear, imbalance, dry tickling throat, clearing throat

  • Eyes- blurred vision, pain, watery or tearing, eyelid twitching, glare hurts, itching, droopy or swollen, redness

  • Respiratory- shortness of breath, coughing, wheezing, mucus, tightness in chest, recurring bronchial infections What the experts say Lilly Byrtus of the Allergy Asthma Information Association recommends, "not having more than 12 houseplants if you are concerned about mold allergies.

Smooth-leaved varieties are better than the fuzzy-leaved ones because the fuzz can end up contributing to the problem when it breaks off or traps dust." Lilly stresses, " it is important to watch the soil. Any sign of mold growth remove the plant." Lilly also recommends plants that like low humidity. Higher humidity may be healthy for many plants but that would include molds and they thrive under higher humidity conditions.

Dr. Stuart Carr, an allergist, says "I have seen patients with indoor plant mold allergies but I don’t see it as a large problem. Houseplants have never been large contributors to the problem of indoor mold sensitivities." Dr. Carr goes on to say that ," the American Thoracic Society says that the data is insufficient to suggest that indoor house plants are the cause of much of indoor mold problems."

Dr. Carr says, "few patients will have major problems from indoor soil molds. Most reactions occur when the patient is repotting or digging in the soil. This stirs up the molds and their spores. Outdoor molds are a much larger problem than indoor molds."

Dr. Carina Majaesic, a pediatric respiratory medicine specialist, sees cases of allergy triggered asthma. She says, "indoor soil molds can contribute to these asthma cases. If the patient tests positive to sensitivity of indoor soil molds, I recommend removal of the plants. The reason for this is that it does not take much of the allergen in a repeated exposure to create a chronic asthma condition." Dr. Majaesic recommends seeing your physician and getting allergy tested if you are in doubt.

Prevention and reducing exposure
The key here is to be vigilant to the appearance of molds on your houseplant soils. The first sign of mold calls for drastic action. Use of a fungicide is an option as is disposal of the plant, in severe cases. Some plant experts recommend using a pea gravel mulch on the top of the soil as a deterrent to molds. Grapefruit seed extract has been used as an effective antifungal. If you have a sensitivity and are repotting use a filter mask to reduce exposure to spores.

Tips for houseplant lovers
Here are a few ideas that may help in avoiding the problem of soil molds from ever starting:

  • choose houseplants that are tolerant of low humidity conditions and require less frequent watering.

Examples of such plants are :

  • Aloe variegata

  • Brassaia actinophylla (Schefflera)

  • Cactus (many species)

  • Crassula argentea (Jade Plant)

  • Dieffenbachia amonena (Dumb Cane)

  • Hoya carnosa (Wax Plant)

  • Philodendron oxycardium (Heartleaf Philodendron)

  • check water requirements of plants carefully. Many will tolerate much less frequent watering in winter.

  • mulch soil surface with pea gravel

Being informed is half the battle when it comes to the problem of indoor soil mold. If you have any questions or are concerned you may have a sensitivity to molds you should see your physician.

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