There is currently no precise information about the prevalence of mould allergies in Germany or the world. This is due in part to the fact that the available skin and blood tests used by doctors to reveal an allergic disposition to mould sometimes deliver contradictory results (see ‘Diagnostic Procedure’ for more information). It has been scientifically demonstrated that people with other respiratory allergies, especially those who suffer from allergic asthma, have a higher risk of reacting to mould.
At the beginning of the 18th century, Sir Floyd made the connection between asthma symptoms and mould long before the term ‘allergy’ even existed. Mould is an organism with a thread-like structure that releases spores in order to reproduce. It spreads in places where damp, organic material is present. Around 107 allergens from 43 different types of mould have been identified so far. The four moulds most frequently associated with allergy symptoms are:
Mould can be found in the atmosphere and in all damp places. Cellars, damp walls, bathrooms, old upholstery, carpets, potting soil, rubbish bins, shower curtains and humidifiers are common sites for mould growth. Regular ventilation and cleaning can help prevent mould formation. One might assume that mould is mainly a problem in old houses, but unfortunately this is not the case. The energy efficiency standards of new buildings have resulted in an optimal indoor climate for mould growth.
Some researchers believe that climate change promotes a higher concentration of airborne spores. For years, experts have observed increasing carbon dioxide (CO2) levels in the air, which is one of the causes of global warming. One study demonstrated that Alternaria moulds release more spores when CO2 levels in the air are higher, and that these spores are even more allergenic than they are at lower CO2 levels.
Mould allergy symptoms often affect the airways and can include nasal congestion and itching, sneezing, coughing, and difficulty breathing. Exposure to mould often aggravates existing asthma symptoms. It can also trigger an atopic eczema flare-up or other skin rashes in people who are sensitised. Although rare, gastrointestinal symptoms may occur after eating spoiled food or foods that have been prepared using mould cultures (blue cheese, for example).
Mould Allergy in Childhood
Various studies indicate an increased risk of mould allergy in children who grow up in a damp, mouldy environment. This is especially the case for families already predisposed to allergies. It is not known whether the risk can be reduced or an allergy can even be prevented by consistently avoiding mould in early childhood. Although there is no precise information regarding prevalence, experts believe that children suffer more frequently from mould allergies than adults. One study on Alternaria moulds demonstrated that antibodies in the blood in early childhood eventually reach a maximum level and then decrease again over time.
Like other allergies, mould allergies are diagnosed in several phases. As a first step, the doctor asks the patient about his or her living conditions and symptoms and tries to identify the possible causes. If a mould allergy is suspected, a skin or blood test is conducted, depending on the symptoms, in order to confirm it. These tests reveal an allergic disposition to certain substances but do not provide evidence of an actual allergy. Tests for diagnosing mould allergies deliver inconsistent results more frequently than for other allergies. The overall consistency rate for both procedures may be lower than 30% depending on the type of mould. There are many reasons for this. In Germany, solutions for around 30 to 40 mould species are available for skin testing. It is very challenging to standardise testing solutions and guarantee their consistent quality, especially for moulds. One of the reasons for this has to do with the actual moulds, since they mutate quickly and constantly adapt to their environments. In doing so, changes also occur in their protein structures, which are critical in allergy testing.
Another difficulty in diagnosing mould allergies is the fact that most patients who react to mould are also allergic to other airborne substances, such as pollen or mites. The symptoms can therefore be masked by another allergy.
This is why an additional diagnostic procedure, the provocation test, is conducted to rule out any doubts. For this test, the patient receives a minute amount of the allergen – for example, on the nasal mucosa. The results confirm whether a specific mould triggers an allergic reaction or whether it can be removed from the list of suspected allergens.
The most effective method for treating a mould allergy is abstention, or allergen avoidance. Depending on the type of mould, it can be difficult to avoid the trigger entirely; it is therefore important to reduce the mould level as much as possible. This means ensuring that there is minimal mould in the living environment. This may include the elimination of houseplants. If such measures do not lead to an improvement in allergy symptoms, medication can be used for relief. There is currently no proven effective immunotherapy for treating the causes of mould allergy.
Prof. Dr. med. Dr. h.c. T. Zuberbier
Last changes made: July 2016
Wiesmüller GA et al. Medizinisch klinische Diagnostik bei Schimmelpilzexposition in Innenräumen. Gesellschaft für Hygiene, Umweltmedizin und Präventivmedizin (GHUP), 2016. Leitlinie gültig bis April 2021.