Studies on dampness and mold in 7127 homes in 22 centers across Europe (including Germany) with on-site inspections in 3118 homes show a self-reported incidence of water damage (10%), damp patches (21%) and mold (16%) that is broadly in line with the observed incidence of dampness (19%) and mold (14%) [1]. Inquiries to health authorities and consumer advice centers show that the occurrence of damp/mold damage in indoor spaces, such as homes, daycare centers, schools, offices, etc., is a significant health issue.

People affected by damp/mold damage indoors are often very unsettled due to incorrect information in the media by some “experts” and also by doctors.

In 2016, the German Society for Hygiene, Environmental Medicine, and Preventive Medicine (GHUP), in collaboration with other scientific medical societies, published the AWMF guideline “Medical clinical diagnostics for indoor mold exposure” for the first time [2] in order to objectify the actual health risks of indoor mold exposure, suitable examination and medical diagnostic methods as well as possible therapies and necessary measures. This was updated in accordance with the AWMF guidelines in 2023 [3].

The key messages of the AWMF mold guideline “Medical clinical diagnostics for indoor mold exposure”—Update 2023 are listed below.

The problem of indoor mold exposure needs to be objectified.

  1. 1.

    Mold infestation to a relevant extent should not be tolerated indoors for precautionary reasons. To assess the extent of damage, please refer to the “Guideline for the prevention, detection and remediation of mold infestation in buildings” published by the Federal Environment Agency [4]. Modified 2023, consensus strength > 95%

  2. 2.

    The most important measures in case of indoor mold infestation are to identify the cause and carry out proper remediation [4]. Checked 2023, consensus strength > 95%

  3. 3.

    For medical indication, indoor mold measurements are rarely useful. As a rule, both a quantitative and a qualitative determination of the mold species can be dispensed with in case of visible mold infestation. Rather, the causes of the infestation should be clarified, and then the infestation and primary causes should be eliminated. Modified 2023, consensus strength > 95%

  4. 4.

    In medical diagnostics for mold exposure, environmental monitoring of mycotoxins in indoor air and house dust has no indication. New 2023, consensus strength > 95%

  5. 5.

    In medical diagnostics for mold exposure, environmental monitoring of microbial volatile organic compounds (MVOC) in indoor air has no indication. New 2023, consensus strength > 95%

  6. 6.

    Exposure to mold can generally lead to irritation of the mucous membranes (Mucous Membrane Irritation, MMI), odor effects and mood disorders. Checked 2023, consensus strength > 95%

  7. 7.

    Special clinical pictures associated with mold exposure relate allergies and mold infections (mycoses). Checked 2023, consensus strength > 95%

  8. 8.

    Physicians shall, in cases of a suspected association between indoor damp/mold damage and conditions for which there is no evidence of such an association (e.g., acute idiopathic pulmonary hemorrhage in children, arthritis, autoimmune diseases, chronic fatigue syndrome (CFS), endocrinopathies, gastrointestinal effects, cancers, airborne mycotoxicoses, multiple chemical sensitivity (MCS), multiple sclerosis, neuropsychological effects, neurotoxic effects, sudden infant death syndrome, renal effects, reproductive disorders, rheumatism, thyroid diseases, sick building syndrome (SBS), teratogenicity and urticaria) inform affected individuals objectively about the current state of knowledge. Modified 2023, consensus strength > 95%

  9. 9.

    Risk groups requiring special protection are:

    1. a.

      Persons under immunosuppression according to the classification of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch-Institute (RKI) [5],

    2. b.

      Persons with severe influenza,

    3. c.

      People with severe COVID-19,

    4. d.

      Persons with cystic fibrosis,

    5. e.

      Persons with bronchial asthma.

    Modified 2023, consensus strength > 95%

  1. 10.

    Individuals who are allergic to mold and those with diseases that weaken the immunological defense system shall be informed about the dangers of mold exposure indoors and about measures to prevent and minimize such exposure. Modified 2023, consensus strength > 95%

  2. 11.

    In principle, a large number of mold species can cause sensitization and allergies in case of corresponding exposure. Compared to other environmental allergens, however, the allergenic potential is to be regarded as lower overall [6, 7]. Modified 2023, consensus strength > 95%

  3. 12.

    As polysensitized individuals, atopic patients often also have IgE antibodies against molds, although this does not necessarily mean that they are ill. The clinical severity of the allergic reaction does not correlate with the level of the specific IgE titer. Modified 2023, consensus strength > 95%

  4. 13.

    The core elements of a type I allergy diagnosis are the medical history, skin prick test, determination of specific IgE antibodies, and provocation testing. In case of allergic bronchopulmonary aspergillosis (ABPA), the determination of specific IgG antibodies should also be performed. In the case of extrinsic allergic alveolitis (EAA), only specific IgG antibodies shall be performed serologically. Modified 2023, consensus strength > 95%

  5. 14.

    The detection of specific IgE or a positive reaction in the skin test initially only means that a specific sensitization to corresponding allergens is present. A clinically relevant allergy only becomes apparent in connection with typical allergic symptoms. Modified 2023, consensus strength > 95%

  6. 15.

    A negative result of a skin test or a specific IgE test for molds does not reliably exclude sensitization to molds. The reasons for this include the varying composition and quality of test extracts or the absence of relevant allergens. Modified 2023, consensus strength > 95%

  7. 16.

    The determination of specific IgG antibodies in connection with the diagnosis of an immediate-type mold allergy (type I allergy) has no diagnostic significance and shall therefore not be performed. This also applies to the detection of immune complexes, e.g., using the Ouchterlony test. Modified 2023, consensus strength > 95%

  8. 17.

    Galactomannan in serum shall only be performed for the diagnosis of suspected invasive pulmonary aspergillosis, otherwise there is no indication in the diagnosis of mold exposure. New 2023, consensus strength > 95%

  9. 18.

    The determination of eosinophil cationic protein (ECP) and β‑1,3‑D-glucan (BDG) in serum has no indication and shall not be performed in medical diagnostics for mold exposure. New 2023, consensus strength > 95%

  10. 19.

    The basophil degranulation test and histamine release (HLT = histamine liberation test), the basophil activation test (BAT) using flow cytometry and the determination of other mediators (sulfidoleukotriene release test, cellular antigen stimulation test (CAST-ELISA)) are used in special diagnostics, but should not be performed in basic allergy diagnostics. New 2023, consensus strength > 95%

  11. 20.

    Lymphocyte transformation tests (LTT) for molds are not indicated as a diagnostic procedure [8] and shall therefore not be performed. Modified 2023, consensus strength > 95%

  12. 21.

    The whole blood test is not a suitable instrument for detecting mold sensitization and shall therefore not be performed. New 2023, consensus strength > 95%

  13. 22.

    Invasive mold infections are rare and are most likely to occur by inhalation. In practice, of the molds classified in risk groups 2 and 3 according to TRBA 460 [9], Aspergillus fumigatus is the most important mycosis pathogen. Individuals with general strong or very strong immune deficiency (according to KRINKO grade 2 and 3 [5]) are predominantly affected. In case of a corresponding disposition, this risk shall be given special attention. Modified 2023, consensus strength > 95%

  14. 23.

    Microbiological, immunological, molecular biological and radiological methods are core elements of mold infection diagnostics and shall be used depending on the indication. Modified 2023, consensus strength > 95%

  15. 24.

    Human biomonitoring of mycotoxins has no indication in medical diagnostics for indoor mold exposure, and shall therefore not be performed. New 2023, consensus strength > 95%

  16. 25.

    The following diagnostic methods shall not be used for indoor mold exposure because there is insufficient scientific evidence (without claim of completeness): Detection of molds in blood, determination of IgA antibodies directed against molds, determination of lymphocyte subpopulations, determination of cytokines, determination of oxidative stress, visual contrast sensitivity test (VCS test), tear film break-up time. New 2023, consensus strength > 95%

  17. 26.

    The following diagnostic methods shall not be used for indoor mold exposure due to a lack of medical and scientific evidence (list is non-exhaustive): Electro-acupuncture according to Voll, bioresonance procedures, pendulum, Vega test, decoder dermography, biotonometry, biotensor, Kirlian photography (plasma print procedure, energetic terminal point diagnosis), regulation thermography according to Rost, auriculodiagnostics, kinesiology, aurascopy, iris diagnostics, cytotoxic blood tests, provocation and neutralization test (PN test). New 2023, consensus strength > 95%

The complete German AWMF guideline “Medical clinical diagnostics for indoor mold exposure”—Update 2023 [3] and an abridged version for those affected by indoor damp/mold damage [10] can be found at: https://register.awmf.org/de/leitlinien/detail/161-001.