How dangerous is mold in the household

Mold in the home causes fear and panic in some households. Hans Peter Seidl is a microbiologist at the Technical University of Munich and a specialist in fungal diagnostics. He is always annoyed at how dubious the subject of mold is treated and how often laypeople are frightened with false statements. "Many purposefully stir up fears through headlines." There is talk of aspergillus from potting soil, which would attack the lungs of an "unsuspecting plant friend", or of "spores from the organic waste bin", which could be a "dangerous time bomb". If you discover mold in your home, you don't usually have to worry about your health right away. However, there are also groups of people for whom an infestation can be dangerous.

"Molds are part of our lives," says Gerhard Wiesmüller, Professor of Hygiene and Environmental Medicine at the Aachen University Hospital. "However, healthy people need not fear that they will make you sick. The probability of this is very low." Mold forms thin threads and spores. The latter are so small that they float in the air over long distances and can be inhaled. Around 200 different types of mold live in Europe. In the house or apartment they form colored, often brown or black spots on walls, ceilings or furniture. "If they grow in secret, you usually only notice them through their smell," says Wiesmüller. "Then it smells musty, musty and quite unpleasant."

British doctor Charles Blackley was believed to be the first to study the health effects of mold. In 1870 he undertook a heroic self-experiment and inhaled mushroom spores. He then got "quite unpleasant complaints," he writes, and wished he hadn't voluntarily exposed himself to it. Researchers paid little attention to the fact that so many mold spores fly around us.

Allergy trigger mold

"When it comes to mold research, we lag quite behind other environmental allergies, such as pollen," says Monika Raulf, scientist at the Institute for Prevention and Occupational Medicine at the Ruhr University in Bochum. The research is more arduous than with other environmental diseases. "On the one hand, the detection of molds is much more complex than of pollen," says Raulf. "And it is also not that easy to establish a connection between the mold and the complaints."

What seems to be clear: Molds can trigger an allergy, which usually manifests itself as hay fever or asthma. The risk is higher if you already suffer from hay fever, neurodermatitis or other allergies. Proteins in the spores or in the threads of the mushrooms act as allergenic substances.

Upon first contact with the fungi, the body becomes sensitized: It forms so-called IgE defense substances against the proteins that bind to certain immune cells (mast cells). With a second or later contact, they release histamine and other messenger substances, which triggers the typical symptoms. Studies show that around five percent of people are sensitized to mold, meaning that IgE can be detected in them. "That is surprisingly little when you consider that 100 to 1000 spores fly around in the indoor air and more than 10,000 spores per cubic meter in the outdoor air, depending on the season and vegetation period," says Raulf.