Understanding mould allergy, severe asthma and Aspergillus-related disease
Asthma with Fungal Sensitisation: Unveiling the Intricacies
Some people with asthma develop an allergic immune response to airborne fungal proteins. This sensitisation may act as an asthma trigger and is more common in difficult or severe asthma, but it is not the same as fungal infection or allergic bronchopulmonary aspergillosis.
- Fungal sensitisation
- SAFS
- Aspergillus
- Alternaria
- ABPA
- Allergy testing
- Antifungals
- Biological therapy
Sensitisation is not infection
A positive fungal allergy test means the immune system recognises a fungal allergen. It does not prove that fungus is invading the lungs or causing every asthma symptom.
ABPA must be considered separately
ABPA is a more specific Aspergillus-related condition involving marked allergic inflammation and characteristic clinical, blood-test or radiological features.
What is asthma with fungal sensitisation?
Asthma with fungal sensitisation describes asthma in a person who has an IgE-mediated immune response to one or more fungal allergens, demonstrated by a positive skin-prick test or allergen-specific IgE blood test.
Fungal spores and fragments are common components of indoor and outdoor air. Most people inhale them without developing asthma symptoms. In a sensitised person, exposure may contribute to airway inflammation, bronchial hyperresponsiveness and variable airflow obstruction.
Fungal sensitisation can occur in mild, moderate or severe asthma. The term severe asthma with fungal sensitisation, or SAFS, is generally reserved for people whose asthma remains severe despite optimised high-level treatment and who have evidence of fungal sensitisation without meeting criteria for ABPA.
Is the person sensitised to a fungal allergen? Is that exposure clinically worsening asthma? Is there a separate Aspergillus-related disease such as ABPA? These questions require different evidence and should not be treated as interchangeable.
How does it differ from other asthma?
| Feature | Asthma without known fungal sensitisation | Asthma with fungal sensitisation | SAFS |
|---|---|---|---|
| Asthma symptoms | Variable wheeze, cough, breathlessness or chest tightness | The same core asthma symptoms | Persistent symptoms or exacerbations despite intensive treatment |
| Fungal allergy test | Negative or not clinically indicated | Positive skin-prick test or fungal-specific IgE | Positive fungal sensitisation testing |
| Asthma severity | May be mild, moderate or severe | May be mild, moderate or severe | Severe asthma after treatment has been optimised |
| ABPA criteria | Absent | Absent unless ABPA coexists | ABPA should be excluded before applying the SAFS label |
| Antifungal treatment | Not indicated for ordinary asthma | Not routinely indicated | May be considered only in selected specialist-managed cases |
Asthma should be confirmed objectively and its severity assessed through a structured review. The London Chest Specialist asthma diagnosis and treatment service explains the usual diagnostic pathway.
Why can fungi aggravate asthma?
IgE-mediated allergy
Fungal allergens can bind to allergen-specific IgE and trigger mast cells, eosinophils and other type-2 inflammatory pathways.
Airway epithelial irritation
Fungal particles and enzymes may irritate or disrupt the airway surface and amplify bronchial inflammation.
Heavy airborne exposure
Damp buildings, decaying vegetation, compost and seasonal spore peaks may increase the amount inhaled.
Airway colonisation
In selected people with structurally abnormal or severely inflamed airways, fungi may persist without necessarily causing invasive infection.
Association does not always prove causation
Fungal sensitisation is associated with poorer asthma outcomes in some populations, but a positive test does not establish that current symptoms are caused by the tested fungus. Viral infection, poor inhaler technique, rhinosinusitis, reflux, smoking, occupational exposure and other factors may be more important.
Fungi linked with asthma sensitisation
Aspergillus fumigatus
A widespread environmental mould and the fungal species most closely associated with ABPA, fungal sensitisation and several other chronic pulmonary conditions.
Alternaria alternata
An important outdoor mould associated with allergic asthma and, in sensitised people, potentially severe seasonal exacerbations.
Cladosporium species
Common outdoor and indoor moulds whose spores may be abundant during warmer months and in damp environments.
Penicillium species
Frequently encountered indoors, particularly where water damage or persistent dampness is present.
Botrytis species
Plant-associated fungi that may contribute to aeroallergen sensitisation in selected individuals.
Trichophyton species
Dermatophytes usually associated with skin infection but capable of producing allergen sensitisation.
Candida species
Yeasts that may generate positive specific-IgE responses, although interpreting their relevance to airway disease can be difficult.
Other moulds
Sensitisation to additional fungi can occur, but test availability, extract quality and clinical relevance vary.
A long fungal allergy panel is not always better
Testing should be selected according to asthma severity, environmental history, geography and the clinical question. Broad panels can identify low-level sensitisation that has little relevance to current symptoms.
Symptoms and clinical clues
Fungal sensitisation does not produce a unique symptom that distinguishes it from other asthma phenotypes. The clues lie in the pattern, severity, triggers and associated test results.
Persistent wheeze
Wheezing may continue despite treatment or recur after exposure to damp environments, decaying vegetation or high outdoor spore levels.
Recurrent asthma attacks
Exacerbations may require repeated oral corticosteroids, emergency care or hospital treatment.
Night symptoms
Nocturnal cough, wheeze or breathlessness can indicate poor asthma control but is not specific to fungal allergy.
Persistent cough
Cough may be dry or associated with mucus. Productive cough raises the possibility of bronchiectasis, infection or ABPA.
Mucus plugs
Thick plugs or bronchial casts are particularly important when ABPA is being considered.
Environmental pattern
Symptoms may worsen in a damp property, during gardening, compost handling or at times of high mould-spore exposure.
Persistent cough should be assessed systematically rather than assumed to result from asthma alone. Read about chronic-cough investigation .
Seek urgent help for a severe asthma attack
Call 999 for severe breathing difficulty, inability to speak in complete sentences, blue or grey lips, exhaustion, confusion, collapse or symptoms that are not improving with the prescribed emergency reliever plan.
How is asthma with fungal sensitisation investigated?
Diagnosis begins by confirming asthma and determining why it is poorly controlled. Fungal sensitisation testing is one component of that assessment rather than a replacement for objective asthma testing.
- Confirm the asthma diagnosis The history is supported with spirometry, bronchodilator reversibility, peak-flow variability, FeNO or bronchial challenge testing where appropriate.
- Assess symptom control and attacks Night symptoms, reliever use, steroid courses, emergency visits and functional limitation are documented.
- Check inhaler technique and adherence Apparently severe asthma may improve substantially when treatment delivery and regular use are corrected.
- Review environmental and occupational exposure Damp, visible mould, water damage, compost, farming, horticulture and workplace exposure are considered.
- Test for fungal sensitisation Skin-prick testing or serum-specific IgE can assess sensitisation to selected fungi.
- Measure inflammatory biomarkers Blood eosinophils, total IgE and FeNO may help characterise type-2 inflammation and guide treatment.
- Assess for ABPA Aspergillus-specific IgE, total IgE, eosinophils, Aspergillus IgG and chest imaging may be required.
- Look for coexisting disease Rhinosinusitis, bronchiectasis, reflux, inducible laryngeal obstruction, obesity, sleep apnoea and infection may contribute.
| Test | What it may show | Important limitation |
|---|---|---|
| Fungal skin-prick testing | Immediate IgE-mediated sensitisation to selected fungal extracts | Antihistamines and extract quality can affect results |
| Fungal-specific IgE | Circulating allergen-specific IgE to selected fungi | A positive result does not prove clinical causation |
| Total IgE | Supports assessment of atopy and forms part of ABPA investigation | It is non-specific and can be raised for many reasons |
| Blood eosinophils | Supports a type-2 or eosinophilic asthma phenotype | Corticosteroids can suppress the count |
| FeNO | Indicates the likelihood of type-2 airway inflammation and corticosteroid responsiveness | It does not identify which allergen is responsible |
| Spirometry | Airflow obstruction and bronchodilator reversibility | Results may be normal between symptomatic periods |
| Chest CT | Bronchiectasis, mucus plugging, infiltrates or another lung disorder | Not required for every person with uncomplicated asthma |
| Sputum fungal culture | Growth of fungi from a respiratory sample | Culture may represent exposure or colonisation rather than active disease |
The role and limitations of airway nitric-oxide measurement are explained in the FeNO testing guide .
Spirometry and additional respiratory physiology can be arranged through the lung-function testing service .
Fungal sensitisation, SAFS and ABPA
Fungal sensitisation
Meaning
A positive fungal skin-prick or allergen-specific IgE test.
Asthma severity
Can occur across the spectrum from mild to severe asthma.
Imaging
No characteristic CT abnormality is required.
Severe asthma with fungal sensitisation
Meaning
Severe asthma accompanied by sensitisation to one or more fungi.
Before diagnosis
Treatment, adherence, exposures and co-morbidities should be optimised and ABPA excluded.
Treatment evidence
Antifungal evidence is limited and management remains specialist and individualised.
Allergic bronchopulmonary aspergillosis
Meaning
A more complex hypersensitivity response to Aspergillus within susceptible airways.
Typical evidence
High total IgE, Aspergillus sensitisation and compatible clinical, radiological or immunological features.
Possible complications
Mucus plugging, recurrent infiltrates and bronchiectasis may develop.
A positive Aspergillus IgE result does not diagnose ABPA
Aspergillus sensitisation is one part of the ABPA assessment. Total IgE, symptoms, eosinophils, imaging and other serological evidence must be interpreted together.
Read the separate London Chest Specialist article on allergic bronchopulmonary aspergillosis .
How is asthma with fungal sensitisation treated?
Treatment starts with evidence-based asthma care. Fungal sensitisation does not replace the need to optimise inhaled treatment, technique, adherence, trigger control and management of coexisting disease.
Inhaled corticosteroid treatment
Corticosteroid-containing inhalers reduce airway inflammation and the risk of asthma attacks. The dose and combination depend on asthma severity.
Combination inhalers
Long-acting bronchodilator and inhaled corticosteroid combinations may improve control when an inhaled corticosteroid alone is insufficient.
MART treatment
An inhaled corticosteroid-formoterol inhaler may be prescribed as both maintenance and reliever therapy for suitable patients.
Biological therapy
Omalizumab, mepolizumab, benralizumab, dupilumab or tezepelumab may be considered according to severe-asthma phenotype and UK eligibility criteria.
Rhinitis and sinus treatment
Nasal corticosteroids, saline irrigation or ENT treatment may reduce upper-airway symptoms that contribute to poor asthma control.
Bronchiectasis management
Airway clearance, sputum cultures and targeted antibiotics may be needed when structural airway disease coexists.
Smoking cessation
Smoking and vaping can worsen symptoms, reduce corticosteroid responsiveness and complicate interpretation of asthma control.
Written asthma action plan
A personalised plan explains regular treatment, signs of deterioration and when urgent help is required.
Biological treatment targets the asthma phenotype
Biologics are not antifungal medicines. They reduce selected allergic or type-2 inflammatory pathways and are prescribed according to asthma severity, biomarkers, exacerbation history and national eligibility criteria.
What is the role of antifungal medication?
Oral triazole antifungal medicines such as itraconazole, voriconazole or posaconazole reduce fungal growth. Their established and potential roles differ between ABPA, chronic pulmonary aspergillosis and SAFS.
| Clinical situation | Usual antifungal approach | Key point |
|---|---|---|
| Fungal sensitisation with otherwise controlled asthma | Antifungals are not routinely indicated | Sensitisation alone does not prove active fungal growth in the airways |
| SAFS | A specialist-supervised trial may occasionally be considered | Evidence is limited and potential benefit must outweigh toxicity and interactions |
| ABPA | Antifungal treatment may be used as part of a broader disease-specific plan | Treatment may also involve corticosteroids or biological therapy |
| Chronic pulmonary aspergillosis | Prolonged antifungal treatment is commonly required | This is a chronic fungal lung infection, not an asthma phenotype |
Antifungal medicines require specialist monitoring
- They can cause liver toxicity.
- They interact with many prescribed medicines.
- Some can raise systemic exposure to inhaled or nasal corticosteroids.
- Drug-level monitoring may be required.
- QT-interval or cardiac assessment may be relevant.
- Fungal resistance and previous azole exposure must be considered.
Do not purchase or start an antifungal independently
Antifungal treatment should follow a defined diagnosis and review of liver function, interactions, pregnancy risk, ECG factors and the intended duration of treatment.
Is fungal allergen immunotherapy used?
Allergen immunotherapy is established for selected pollens, dust mites and other allergens in appropriate patients. Evidence, standardisation and safety information for mould immunotherapy are more limited.
It is not routine treatment for severe fungal-sensitised asthma
Allergen immunotherapy should not be assumed to be appropriate merely because a fungal allergy test is positive. Uncontrolled or severe asthma also increases the risk of systemic reactions to immunotherapy.
Reducing damp and mould exposure
Reducing significant damp and visible mould is sensible for respiratory health, but environmental measures should complement prescribed asthma treatment rather than replace it.
Repair water leaks
Address leaking roofs, pipes, windows and appliances rather than repeatedly cleaning the visible surface alone.
Improve ventilation
Use extractor fans when cooking or bathing and ventilate rooms without allowing them to become excessively cold.
Manage condensation
Maintain appropriate heating, avoid drying large quantities of laundry indoors and reduce persistent window condensation.
Control indoor humidity
A dehumidifier may help selected homes, but the underlying source of moisture should still be addressed.
Handle compost carefully
Compost, decaying leaves and soil can release high concentrations of fungal spores when disturbed.
Review occupational exposure
Farming, horticulture, waste management, baking and damp buildings may create clinically relevant exposure.
Avoid unsafe mould-removal practices
Large areas of mould, sewage contamination or major water damage may require professional remediation. Scrubbing extensive mould without suitable protection can aerosolise spores and worsen exposure.
Monitoring and follow-up
Asthma symptoms
Daytime symptoms, night waking, activity limitation and reliever use are reviewed over time.
Exacerbation frequency
Steroid courses, urgent appointments, emergency visits and hospital admissions help define severity.
Lung function
Spirometry and peak-flow trends can document variable obstruction and detect deterioration.
Inflammatory markers
Eosinophils, FeNO, total IgE and allergen-specific IgE are used selectively according to the clinical question.
Imaging changes
Repeat imaging may be appropriate when ABPA, bronchiectasis, mucus plugging or another structural condition is present.
Treatment toxicity
Blood tests, ECGs, drug levels or interaction reviews may be needed during antifungal or biological treatment.
Asthma can overlap with bronchiectasis, rhinosinusitis, reflux, infection and ABPA. The article on bronchiectasis and co-morbidities explains how these treatable traits can be assessed separately.
When should medical help be sought?
Arrange specialist review when:
- asthma remains uncontrolled despite regular treatment;
- several oral-steroid courses are needed each year;
- symptoms repeatedly worsen in damp or mouldy environments;
- there is persistent mucus production or recurrent infection;
- thick mucus plugs or bronchial casts are produced;
- blood tests show high IgE or eosinophils;
- chest imaging shows bronchiectasis or changing infiltrates;
- ABPA or SAFS has been suggested.
Call 999 for:
- severe breathing difficulty;
- inability to speak in complete sentences;
- blue or grey lips or skin;
- exhaustion, confusion, collapse or fainting;
- rapidly worsening symptoms despite following the emergency asthma plan;
- significant coughing of fresh blood;
- severe chest pain or another immediately life-threatening symptom.
Conclusion
Asthma with fungal sensitisation describes asthma accompanied by an IgE-mediated response to one or more fungal allergens. It does not automatically mean that fungus is infecting the lungs.
Sensitisation may contribute to wheeze, cough, breathlessness and exacerbations, but symptoms overlap with many other causes of poor asthma control.
SAFS is generally reserved for severe asthma with fungal sensitisation after treatment has been optimised and ABPA has been excluded.
ABPA is a separate Aspergillus-related disease requiring compatible clinical, immunological and often radiological evidence. A positive Aspergillus allergy test alone is insufficient.
Treatment begins with high-quality asthma care: corticosteroid- containing inhalers, correct technique, good adherence, a written action plan and management of environmental and coexisting factors.
Biological therapy may help an eligible severe-asthma phenotype. Antifungal medicines are not routine treatment for sensitisation alone and should be prescribed only after specialist assessment.
People with difficult asthma, recurrent steroid treatment, Aspergillus sensitisation, mucus plugging or possible ABPA can arrange a specialist asthma assessment .
Frequently asked questions
What does fungal sensitisation mean?
It means that a skin-prick test or blood test has identified an IgE-mediated immune response to a fungal allergen.
Does fungal sensitisation mean that I have a fungal infection?
No. Allergy, airway colonisation and fungal infection are different biological states and require different evidence.
What is SAFS?
SAFS means severe asthma with fungal sensitisation. It is generally considered after asthma treatment has been optimised and ABPA has been excluded.
Is SAFS the same as ABPA?
No. ABPA has a more specific immunological and clinical syndrome and may cause mucus plugging, infiltrates and bronchiectasis.
Can a positive Aspergillus IgE test diagnose ABPA?
No. It confirms sensitisation. Total IgE, eosinophils, symptoms, imaging and other investigations are also needed.
Which fungi are most often linked with asthma?
Commonly tested fungi include Aspergillus, Alternaria, Cladosporium and Penicillium. Other fungal allergens may also be relevant.
Does every sensitised patient need antifungal treatment?
No. Antifungals are not routine treatment for sensitisation alone and carry important risks and interactions.
Can biological medicines treat SAFS?
Biological therapy may be appropriate when the patient meets severe-asthma criteria for an allergic, eosinophilic or other eligible inflammatory phenotype.
Should I remove indoor plants?
Not automatically. Visible mould, persistently damp compost or a reproducible symptom pattern may justify reducing exposure, but the whole indoor environment should be assessed.
Can mould in a home cause asthma?
Damp and mould exposure is associated with respiratory symptoms and asthma morbidity. Individual causation can be difficult to prove, but significant damp should be corrected.
Can fungal sensitisation cause night-time asthma?
It may contribute, but night symptoms also occur with poorly controlled asthma, rhinitis, reflux, sleep apnoea and several other conditions.
Is fungal allergy testing affected by medication?
Antihistamines can suppress skin-prick responses. They do not usually invalidate serum-specific IgE testing. Follow the testing service’s instructions.
Should asthma inhalers be stopped before testing?
Do not stop prescribed asthma treatment unless the respiratory laboratory or clinician has given specific instructions.
Can fungal sensitisation coexist with bronchiectasis?
Yes. Bronchiectasis, asthma, fungal sensitisation and ABPA can overlap and require careful interpretation of CT, blood tests and sputum microbiology.
References and further information
- National Institute for Health and Care Excellence. Asthma: diagnosis, monitoring and chronic asthma management. NICE guideline NG245. View the NICE asthma guideline
- National Institute for Health and Care Excellence. Managing difficult and severe asthma. View the NICE severe-asthma pathway
- British Thoracic Society. Clinical Statement on Aspergillus-related chronic lung disease. 2025. View the BTS clinical statement
- London Chest Specialist. Asthma diagnosis and treatment. Read about specialist asthma assessment
- London Chest Specialist. Allergic bronchopulmonary aspergillosis. Read the ABPA guide
- London Chest Specialist. Fractional exhaled nitric oxide: a quick guide. Read about FeNO testing
- London Chest Specialist. Lung-function tests. Read about spirometry and respiratory physiology
- London Chest Specialist. Bronchiectasis diagnosis and treatment. Read about bronchiectasis care
- London Chest Specialist. Living with bronchiectasis and co-morbidities. Read about overlapping asthma, ABPA and bronchiectasis
