not-yet-known not-yet-known not-yet-known unknown Background: Fungal aeroallergen (mould) sensitisation is associated with poor control in children, particularly amongst low-income and ethnic minority groups. However, its association with deprivation and ethnicity remains unclear. Objective: To determine whether fungal sensitisation is associated with deprivation and ethnicity in children with difficult-to-treat asthma. Methods: Cross-sectional analysis of difficult-to-treat asthmatic children (5-16 years) referred to a regional severe asthma centre between 2018 and 2024. All eligible patients were prescribed high dose inhaled corticosteroids. Socioeconomic status was assessed using index of multiple deprivation deciles (IMDD) based on patient postcodes. Logistic regression was used to identify predictors of fungal sensitisation. Results: Of 89 difficult-to-treat asthmatics, median age was 10.5 years (IQR 5.5-16.0), 61 (68.5%) were male and 45 (50.6%) were non-Caucasian. 43 (48.3%) were fungal sensitised, with higher non-Caucasian representation in the sensitised group (67.7% vs 39.5%, p<0.05). Logistic regression identified IMDD, but not ethnicity, as a significant predictor of fungal sensitisation (IMDD OR: 1.29, p<0.05; non-Caucasian ethnicity OR: 2.87, p=0.088). Conclusions: Socioeconomic deprivation was the strongest predictor of fungal sensitisation in this cohort while ethnicity displayed a non-significant trend as a possible risk factor . However, children from ethnic groups were disproportionately represented among the fungal sensitised group. Targeted interventions to improve the indoor environment in vulnerable populations may improve asthma control. Further research into the mechanisms driving fungal sensitisation in these groups has the potential to inform preventative and therapeutic interventions.