Clinical findings and subjective symptoms in patients with bronchial asthma and chemical hypersensitivity in Japan.

Background: Despite advances in pharmacologic therapy, a subset of patients with bronchial asthma (BA) experience persistent symptoms. Multiple chemical sensitivity (MCS), a non-allergic condition triggered by low-level chemical exposures, may be responsible for asthma-like symptoms. Although epidemiological studies have reported a high co-prevalence of MCS and BA, clinical comparisons among patients with BA between those with and without MCS are limited. We aimed to characterize the clinical and symptomatic profiles of patients with BA and comorbid MCS.

Methods: This cross-sectional study included 100 patients with BA treated at Sagamihara Hospital. MCS-related symptoms were evaluated using the Quick Environmental Exposure and Sensitivity Inventory (QEESI). Clinical data including serum total Immunoglobulin E (IgE) levels, eosinophil counts, pulmonary function, hospitalization frequency, comorbidities, and medications were collected by attending physicians. Fifteen patients who exceeded the QEESI MCS cut-off value (BA-MCS group) were compared with 30 age- and sex-matched controls without MCS (BA-control group).

Results: Compared to BA-controls, the BA-MCS group had strong symptoms in multiple organs other than the respiratory system (p = 0.000), exhibited significantly higher percentage forced expiratory volume (%FEV₁) (p = 0.047), lower serum IgE levels (p = 0.028), more frequent hospitalizations (p = 0.002), and higher incidence of atopic dermatitis history (p = 0.001).

Conclusions: The BA-MCS group had a distinct phenotype characterized by preserved lung function, low IgE levels, systemic symptoms, and high disease burden. For these patients, a multidisciplinary approach addressing BA and MCS may be more effective than intensifying asthma pharmacotherapy alone.