Airborne Allergens and Air Pollutants Often Trigger Asthma and Nasal Congestion

A good review of the effects of allergens and pollutants in the air in causing or worsening asthma and nasal problems is found in the February 2010 Journal of Asthma and Clinical Immunology.  Many studies have linked exposure to indoor or outdoor molds (fungi) to higher incidence and/or worsening symptoms in those with asthma and wheezing.

Over 200 allergens from common mold genera such as Cladosporium, Penicillium, Aspergillus, Alternaria, Fusarium and yeasts have already been identified. The allergens from the Alternaria mold are believed to be especially bad in triggering asthma in sensitive individuals.  To prevent mold growth in homes, all signs of visible mold should be cleaned immediately. Water problems such as flooding and pipe leaks should also be fixed immediately to control mold growth. Several studies have reported that fixing mold and water problems in homes and schools can significantly reduce breathing problems in asthmatics.

Outdoor pollens are also major triggers for asthma and nasal congestion (rhinitis).   Particularly bad pollens include tree pollens (in early to mid spring) and pollens from grasses and ragweeds (mid summer to the first hard frosts of fall). Anti-histamine medication and sublingual (under the tongue) pollen immune therapy is helpful in reducing allergic problems in many pollen allergic people.

Allergens from many animals including dust mites, cockroaches, pigeons, rats, mice, dogs and cats can also worsen asthma and rhinitis.  Dust mite growth can be reduced by keeping home relative humidity below 60% with air conditioners and dehumidifiers.  Encasing pillows and bedding with anti-mite materials and washing this bedding regularly in hot water can also reduce dust mite allergens in the bedrooms. Cockroach populations can be kept down by keeping kitchens clean, cleaning up spilled food, and using flypaper and less toxic pesticides (like boric acid) to control cockroaches.  Cat allergens can be reduced by over 90% by bathing the cat every month (if the cat will tolerate bathing).

Many air pollutants can trigger asthma and nasal problems. Low levels of particulate matter, ozone and carbon monoxide  in the air can worsen asthma. Several studies have shown that the presence of low to moderate levels of air pollution (such as particulates or ozone) can make a person more sensitive to the adverse health effects of airborne allergens such as molds and pollens.  Wood burning fireplaces and the outdoor burning of leaves, trash and grass can significantly increase both air pollution levels and rates of asthma.

I have written a review of the health effects of outdoor air pollution.  For a free pdf copy of this review, please contact me at

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