Microbes are a part of our normal environment and can be both beneficial and detrimental to our health.
"Exposure to microbes in childhood can prevent the development of allergies. On the other hand, mould growth can increase the risk of asthma," said Dr Helena Rintala from the National Institute for Health and Welfare in Finland.
In indoor environments microbes thrive on surfaces that are occasionally moist or wet, for example in the kitchen and bathroom. Prolonged damp anywhere in the house can lead to greater numbers of microbes.
"These microbes, their spores and the molecules they secrete can be released into the air which can lead to health problems if they are breathed in," she said.
Dr Helena Rintala, described it at the Society for General Microbiology's autumn meeting in Nottingham.