Last reviewed: 11 March 2026

Severe Asthma with Fungal Sensitisation (SAFS)

Overview

Severe Asthma with Fungal Sensitisation (SAFS) is a condition seen in some people with severe asthma whose immune system reacts strongly to fungal allergens in the air.

Fungal spores are present almost everywhere, both indoors and outdoors. Common fungi linked with airway allergy include Aspergillus, Alternaria, Cladosporium and Penicillium. Most people breathe in fungal spores every day without becoming ill, but in some people with asthma, the immune system becomes sensitised to them. This means the body treats the fungal proteins as allergens and triggers airway inflammation.

SAFS is not the same as ABPA. In SAFS, there is severe asthma plus fungal sensitisation, but without the fuller pattern of immune overreaction and lung changes that define ABPA, such as very high total IgE levels, mucus plugging, or bronchiectasis typical of ABPA.

SAFS is often described as part of a spectrum:

• asthma with fungal allergy,
• severe asthma with fungal sensitisation (SAFS),
• allergic bronchopulmonary aspergillosis (ABPA).

Not everyone moves along this spectrum. Many people remain stable within one category.

Symptoms

The symptoms of SAFS are usually those of severe, difficult-to-control asthma. They may include:

• wheezing,
• shortness of breath,
• chest tightness,
• persistent cough,
• frequent flare-ups or “exacerbations”,
• night-time symptoms,
• poor response to usual asthma treatment.

Some people notice that their symptoms worsen in certain environments, such as damp buildings, mouldy rooms, when gardening, or around compost and decaying plant material. However, this is not true for everyone, and it can be difficult to prove exactly how much environmental fungal exposure is contributing in an individual case.

Diagnosis

There is no single test that proves SAFS. Diagnosis is usually made by looking at the whole clinical picture and excluding other fungal-related lung conditions, especially ABPA.

Typical features used in diagnosis include:

• severe asthma that remains poorly controlled despite appropriate treatment, usually including high-dose inhaled corticosteroids and long-acting bronchodilators,
• fungal sensitisation, shown by a positive skin prick test or blood test for fungus-specific IgE,
• absence of ABPA based on clinical assessment, blood tests, and imaging.

Tests that may be used include:

• lung function tests,
• blood tests such as total IgE, eosinophils, and fungus-specific IgE,
• skin prick allergy testing,
• chest X-ray or CT scan if needed to look for bronchiectasis, mucus plugging, or other diagnoses.

Because SAFS overlaps with other types of severe asthma and fungal-related disease, specialist assessment is often helpful.

Causes

SAFS is thought to result from an allergic immune response to inhaled fungi in someone who already has severe asthma. It is not usually described as an invasive fungal infection.

In simple terms:

1. fungal spores are breathed into the airways,
2. the immune system recognises them as allergens,
3. the airways become inflamed,
4. asthma symptoms become more severe and harder to control.

Some researchers think that in a proportion of patients, fungi may do more than simply trigger allergy, and may persist in airway mucus or interact with the airway lining in ways that worsen inflammation. This is still an area of ongoing research, which is one reason why SAFS remains a slightly uncertain diagnosis compared with better-defined conditions such as ABPA.

Possible contributing factors include:

• having severe asthma already,
• Type 2 (T2) airway inflammation,
• environmental exposure to mould or heavy fungal spore loads,
• poor airway clearance or mucus retention in some patients.

Treatment

Treatment usually starts with best-practice severe asthma care. The exact combination depends on the person’s asthma pattern, test results, symptoms, and response to previous treatment.

1. Optimising asthma treatment

This often includes:

• high-dose inhaled corticosteroids,
• long-acting bronchodilators,
• careful inhaler technique review,
• checking adherence and trigger exposure,
• management of related problems such as rhinitis, reflux, or dysfunctional breathing.

2. Oral steroids

Short courses of oral corticosteroids may be needed during severe asthma flare-ups. Some people with very difficult asthma may remain on maintenance oral steroids, but this is generally avoided where possible because of the risk of long-term side effects.

3. Biologic medicines

Biologics are increasingly important in the treatment of severe asthma, including in some patients with SAFS. Which biologic is chosen depends on the person’s asthma phenotype, including IgE level, eosinophil count, exacerbation history, and other features.

Examples include:

• omalizumab – targets IgE,
• mepolizumab – targets interleukin-5,
• benralizumab – targets the interleukin-5 receptor,
• dupilumab – targets interleukin-4/interleukin-13 signalling,
• tezepelumab – targets thymic stromal lymphopoietin (TSLP).

Although SAFS was originally discussed mainly in relation to omalizumab and antifungals, modern severe asthma care increasingly involves a wider choice of biologics.

4. Antifungal treatment

Some studies have suggested that antifungal medicines such as itraconazole may improve symptoms or quality of life in selected patients with SAFS. However, antifungal treatment is not automatically recommended for everyone.

Reasons for caution include:

• benefit is variable,
• azole antifungals can interact with many other medicines,
• monitoring is often needed for liver function and drug levels,
• the evidence base is still limited compared with standard severe asthma treatments.

If antifungals are considered, this is usually best done by a specialist team familiar with both severe asthma and aspergillosis-related disease.

5. Reducing fungal exposure

Heavy indoor mould exposure may worsen symptoms in some people. Practical steps may include:

• repairing leaks and damp problems,
• improving ventilation,
• reducing condensation,
• avoiding obvious mould growth,
• being cautious with compost, mulch, or rotting plant matter if these trigger symptoms.

It is usually not realistic or helpful to try to avoid all fungal exposure, because fungi are a normal part of the environment.

Prognosis

SAFS can make asthma more difficult to control and may be associated with more flare-ups and worse quality of life. However, the outlook varies a lot from person to person.

Many patients improve when their asthma is assessed carefully in a specialist clinic and treatment is tailored properly. This may include inhaler optimisation, biologic therapy, and in selected cases antifungal treatment.

Unlike ABPA, SAFS does not usually imply the same degree of structural lung damage. However, severe asthma itself can still have a major impact on daily life, sleep, work, and wellbeing.

Common questions

Does SAFS mean I have a fungal infection in my lungs?

Usually, no. SAFS is generally understood as severe asthma plus fungal allergy, rather than an invasive or destructive fungal infection.

Is SAFS the same as ABPA?

No. Both involve reactions to fungi, often Aspergillus, but ABPA has a more specific pattern including stronger immune activation and often characteristic scan or mucus-plugging changes.

Can SAFS turn into ABPA?

These conditions sit on a spectrum, but not everybody progresses. Some patients remain stable with SAFS and never develop ABPA.

Will antifungals definitely help?

Not necessarily. Some people improve, while others do not. Antifungals need careful consideration because they can cause side effects and drug interactions.

Are biologics relevant in SAFS?

Yes. Because SAFS sits within severe asthma care, biologics are often an important part of treatment when the asthma phenotype fits.

When to seek medical advice

Seek medical advice promptly if you have:

• asthma that remains poorly controlled despite regular treatment,
• frequent steroid-requiring flare-ups,
• worsening wheeze, breathlessness, or cough,
• suspected mould exposure that seems to worsen symptoms,
• concerns about side effects from steroids, biologics, or antifungal medicines.

Seek urgent help if you have severe breathlessness, difficulty speaking in full sentences, blue lips, confusion, or a rapid worsening of asthma symptoms.

Further information

You may also find these pages helpful:

• Allergic Bronchopulmonary Aspergillosis (ABPA)
• Aspergillus bronchitis
• Asthma and aspergillosis
• Biologics and aspergillosis

Author and review information

References

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