Molds are small organisms found almost everywhere, both indoors and outdoors. No one knows for sure how many species exist, but the estimates are in the hundreds of thousands. Molds grow best in warm, damp conditions and spreads by making spores. The spores can survive harsh conditions and can be extremely difficult to get rid of.
Over the past decade, studies have increasingly shown a direct link between mold and upper respiratory infections. A 1999 Mayo Clinic study found that nearly all chronic sinus infections (afflicting 37 million Americans) are the result of exposure to mold. In 2004, the Institute of Medicine (IOM) found there was sufficient evidence to link indoor exposure to mold with upper respiratory symptoms in otherwise healthy people; with asthma symptoms in those suffering from asthma; and cases of pneumonia in individuals with compromised or weakened immune symptoms. In 2009, the World Health Organization (WHO) issued guidelines on mold exposure, citing numerous studies linking mold to a variety of conditions including asthma, sinusitis, and allergic reactions.
Depending on the type and quantity of mold, a wide variety of adverse reactions can be experienced. Any type of mold can cause allergic reactions in sensitive individuals. The most common symptoms of allergic reaction to mold include sneezing, coughing, itchy-watery eyes, and throat irritation.
Exposure to mold is far more common than many people think. According to a 1994 Harvard study of 10,000 homes in the United States and Canada, half had conditions of water damage and mold associated with a 50-100% increase in respiratory symptoms. Toxic mold is an increasing problem in homes and businesses these days, but even the more common forms of mold can cause allergic reactions, respiratory distress, and illness in individuals.