Actinomycetes symptoms: what can they cause?

Exposure to actinomycetes is most often linked to airway symptoms: cough, a blocked or runny nose, an irritated throat and repeated sinus infections. Many people also have fatigue, headaches and a general feeling of being unwell.

None of these symptoms is caused by actinomycetes alone. Actinomycetes almost always grow in the same water damage as moulds and other microbes, and symptoms come from the whole mixture. So the most useful question is not “is this actinomycetes?” but “do my symptoms follow a particular building?”

Actinomycetes are soil bacteria that look like mould and smell like an earth cellar. This article focuses on symptoms: what is known about them, how certain that knowledge is, and what you can do.

What are the symptoms of actinomycetes exposure?

The table lists the symptoms found most often in people who spend time in water-damaged buildings. Actinomycetes are part of the microbial mix in these buildings.

Body area	Typical symptoms	How certain?
Nose and sinuses	Blocked or runny nose, repeated sinus infections, dry nose	Well studied for water damage [1, 2]
Throat and lungs	Cough, wheezing, shortness of breath, worsening asthma, repeated airway infections	Well studied for water damage [1, 2]
Skin	Rash (eczema)	A link with water damage has been found [1]
Whole body	Fatigue, headaches, brain fog, feeling unwell	Preliminary research [3]
Lungs (rare)	Fever, chills, cough and breathlessness a few hours after exposure	Well known, but almost always from farm hay dust [5, 6]

Brain fog means your thinking feels slow and foggy: words do not come and you lose focus easily.

In Anna’s story the key clue is not any single symptom. It is that her symptoms eased away from home and came back when she returned.

What does research say about actinomycetes symptoms?

Water damage and mould have been studied a lot in people. Actinomycetes on their own have been studied very little.

Well studied Indoor dampness and mould are linked to asthma, cough, wheezing, shortness of breath, airway infections, allergic rhinitis, eczema and upper-airway symptoms. A large review brought this together from many population studies. The link was seen in both allergic and non-allergic people [1]. The World Health Organization (WHO) reached the same conclusion [2].

One small study A Finnish study looked at 39 badly water-damaged family homes, 71 adults and 68 children. The researchers grew microbes from building material samples and compared the amounts with the residents’ symptoms [3]:

• In the homes whose materials had the most actinomycetes, adults had more general symptoms, rated their health as worse, and their lung function varied more from day to day.
• In children, the homes with the most actinomycetes were linked to lower-airway symptoms such as cough and wheezing.
• The researchers stress that the results were very uncertain. The groups were small.

So far this is the clearest study in people in which actinomycetes were measured separately.

Preliminary research Other evidence comes from cell and animal studies. Streptomyces actinomycetes taken from the indoor air of mouldy houses triggered inflammation in mouse lungs and in human lung cells [7, 8]. This explains why symptoms can arise, but not how often people become ill.

Why can actinomycetes cause symptoms?

When you breathe indoor air, you also breathe small particles: actinomycete spores, fragments of them and the substances they produce. Your immune system checks them.

Your body also reacts to dead microbes and their fragments. That is why killing the microbes does not remove the symptoms; the damaged material has to be removed. Read more about the difference between active, dead and dormant mould.

How can you tell actinomycetes symptoms from a cold or an allergy?

The symptoms themselves look like a cold or an allergy. The difference is how they behave over time and from place to place.

	Cold	Pollen allergy	Water-damage symptoms
How long	1–2 weeks	Seasonal, for example in spring	Weeks or months
Where	Does not depend on place	Worse outdoors	Worse in one building
Away from home	No effect	No effect	Often eases within days or weeks
Fever	Often	No	Usually not
Other family members	Catch it	Only those with the allergy	Some may have symptoms, others not

Can actinomycetes cause a fever?

Usually not. Fever is linked to one rare lung disease: hypersensitivity pneumonitis, also called extrinsic allergic alveolitis. The tiniest parts of the lungs become inflamed when a person repeatedly breathes large amounts of organic dust.

The best-known form is farmer’s lung. Its most common causes include heat-loving actinomycetes that grow in damp hay and grain [6]. Symptoms are fever, chills, cough and shortness of breath, typically starting 4–8 hours after exposure [5].

In a water-damaged home this is rare. If you repeatedly get a fever and shortness of breath in a particular place or after a particular job, see a doctor. Hypersensitivity pneumonitis is treatable, and the most important treatment is ending the exposure [6].

Is there a blood test or other test for actinomycetes?

There is no reliable test that tells you whether actinomycetes are causing your symptoms.

• Antibody studies: In a Finnish study, people who spent time in microbe-rich buildings had more IgG antibodies to spores of the actinomycete Streptomyces albus than people in comparison buildings [9]. But antibodies only show that your body has met the microbe, not that it is making you ill.
• Doctors’ guidance: According to German guidance for doctors, blood or urine tests for mould components are generally not part of investigating symptoms. The work-up starts with your history, an examination and, where needed, allergy tests [4].

It is more important to investigate the building. Actinomycetes are found in building material samples by culture or DNA methods. They do not show up in the popular ERMI and HERTSMI-2 dust tests, which measure only moulds. Read more about how actinomycetes are found in a building.

How do you know whether your symptoms come from your home?

Timing tells you more than any single symptom. Try this:

When you come home after a few days away, sniff the air as soon as you open the door. Your nose quickly gets used to a familiar smell, but after a break you notice an earthy, cellar-like smell more easily. Read also about the signs of water damage at home.

Why do symptoms continue for some people after moving?

For most people, symptoms ease once the exposure ends. For some, they continue for months even after they have left the building.

Expert view In Dr Ritchie Shoemaker’s model, this long-lasting, multi-system picture is chronic inflammatory response syndrome, CIRS. According to the model, the body of a genetically susceptible person cannot clear the toxins of microbes from water-damaged buildings (biotoxins), and the inflammation stays switched on [10]. Actinomycetes are part of this microbial mix. Their share in CIRS has not been studied separately, and mainstream medicine has not accepted CIRS as a diagnosis.

If your symptoms continue after the exposure has ended, read what triggers CIRS and how CIRS is diagnosed.

What should you do if you suspect actinomycetes symptoms?

Remember these

Test yourself: Can you explain why a symptom diary tells you more than a blood test? And why a clean HERTSMI-2 result does not rule out actinomycetes?

What next?

• Read the actinomycetes guide: what they are, how they smell and how they are removed.
• Read about water damage symptoms in the home and in people.
• Read what CIRS is.

References

1. Mendell MJ, Mirer AG, Cheung K, Tong M, Douwes J. Respiratory and allergic health effects of dampness, mold, and dampness-related agents: a review of the epidemiologic evidence. Environ Health Perspect. 2011;119(6):748–756. PubMed
2. World Health Organization. WHO guidelines for indoor air quality: dampness and mould. Copenhagen: WHO Regional Office for Europe; 2009. WHO
3. Järvi K, Hyvärinen A, Täubel M, et al. Microbial growth in building material samples and occupants’ health in severely moisture-damaged homes. Indoor Air. 2018;28(2):287–297. PubMed
4. Hurraß J, Nowak D, Heinzow B, Joest M, Stemler J, Wiesmüller GA. Indoor mold—important considerations for medical advice to patients. Dtsch Arztebl Int. 2024;121(8):265–271. PubMed
5. MSD Manual Consumer Version. Hypersensitivity pneumonitis. Accessed 8 November 2026. msdmanuals.com
6. Cano-Jiménez E, Acuña A, Botana MI, et al. Farmer’s lung disease. A review. Arch Bronconeumol. 2016;52(6):321–328. PubMed
7. Jussila J, Komulainen H, Huttunen K, et al. Inflammatory responses in mice after intratracheal instillation of spores of Streptomyces californicus isolated from indoor air of a moldy building. Toxicol Appl Pharmacol. 2001;171(1):61–69. PubMed
8. Jussila J, Ruotsalainen M, Komulainen H, et al. Streptomyces anulatus from indoor air of moldy houses induce NO and IL-6 production in a human alveolar epithelial cell-line. Environ Toxicol Pharmacol. 1999;7(4):261–266. PubMed
9. Atosuo J, Karhuvaara O, Suominen E, Vilén L, Nuutila J, Putus T. Indoor exposure to Streptomyces albus and Aspergillus versicolor elevates the levels of spore-specific IgG, IgG1 and IgG3 serum antibodies in building users – a new ELISA-based assay for exposure assessment. Sci Total Environ. 2020;698:134335. PubMed
10. Shoemaker RC, House DE. Sick building syndrome (SBS) and exposure to water-damaged buildings: time series study, clinical trial and mechanisms. Neurotoxicol Teratol. 2006;28(5):573–588. PubMed