Allergens and viruses act together to worsen asthma

Common allergens (such as dust mite and grass pollen) and viruses may act together to exacerbate asthma, concludes a study in this week’s BMJ.

Sixty patients (aged 17 to 50) admitted to hospital over a year with acute asthma were matched with two controls: patients with stable asthma and patients admitted to hospital with non-respiratory diseases (inpatient controls). Skin tests for dust mite, cat, dog, and grass allergens were performed on all patients.

A significantly higher proportion of patients admitted with asthma (66%) were both sensitised and exposed to allergen causing sensitisation (either mite, cat, or dog) than patients with stable asthma (37%) and inpatient controls (15%).

Viruses were detected in 26% of patients admitted with asthma compared to 18% with stable asthma and 9% of inpatient controls. This suggests that patients with asthma may be more susceptible to viral infections than patients without asthma, say the authors.

Allergens and viruses may act together to exacerbate asthma, indicating that domestic exposure to allergens acts synergistically with viruses in allergic patients, increasing the risk of hospital admission, say the authors. Strategies directed at viruses and reducing exposure to allergens are needed, they conclude.