© by aha! Swiss Allergy Centre - Info on allergies - Mould allergy - Penicillium

Moulds are thread-like micro-fungi – they occur all over the world and grow particularly in places where there is moisture. If living spaces are infested with mould, it must be removed quickly. It may pose a health risk.

Triggers of mould allergy

The most important known allergens among fungi are Aspergillus species, Alternaria alternata, Cladosporium species and Penicillium species, which all belong to the category of moulds. Moulds are found all over the world, but predominantly in nature, mainly in the soil, in dead organic matter. Indoors moulds develop in places where it is damp, such as areas affected by leaks, in masonry cracks or when the relative air humidity is high. Poorly maintained ventilation systems, air humidifiers or decorative fountains and a lot of plants in a room can also lead to a mould infestation.


Mould allergy, like other respiratory allergies, is manifest as allergic runny nose, streaming eyes, cough and shortness of breath and is frequently accompanied by asthma. As well as allergic reactions, moulds also cause irritation of the airways, the mucous membranes of the eyes and the skin. 

The growth of mould is often associated with a distinctively musty smell of earth, damp and mushrooms, which additionally impairs well-being.

Diagnosis and differential diagnosis

It is not easy to make the diagnosis because there is a lack of good allergen extracts. Nevertheless, investigations with an allergy specialist are important so that a diagnosis can be made and possible treatment measures decided.

Therapy and treatment

Any fungal infestation in living areas must be removed rapidly and properly. It is always important to get rid of the cause, hence eradicate the damp problem. Otherwise the mould will quickly reappear. People with health problems should not remove even small patches of mould growth. Before the mould is cleared and in the weeks following its clearance, rooms should also be aired frequently and dust should be removed.

Tips and tricks:

  • keep relative air humidity to a maximum of 45 per cent in winter
  • keep temperature between 19 and 23°C in winter
  • air rooms thoroughly for five to ten minutes twice to three times a day
  • position furniture at least ten centimetres away from walls
  • no plants in the bedroom area
  • dispose of compost or organic waste on a daily basis or store temporarily outside the home
  • do not use air humidifiers or only use them if air humidity is continuously monitored

Facts and figures

It is estimated that about one to ten per cent of the Swiss population are sensitized to moulds.

Editors: aha! Swiss Allergy Centre in co-operation with the Scientific Advisory Board. For prevalence figures, see source references.

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