Allergen‐induced increase in non‐allergic bronchial reactivity

TLDR

Non‑allergic bronchial hyper‑reactivity is common in most asthma patients. The study measured histamine and methacholine‑induced bronchial reactivity in 13 asthmatics before and after laboratory allergen exposure. Allergen exposure triggered early and late asthmatic responses and increased non‑allergic bronchial reactivity in seven of 13 patients for up to a week, indicating that allergens exacerbate asthma partly through non‑allergic pathways and that avoidance can reduce hyper‑reactivity.

Abstract

Non-allergic bronchial hyper-reactivity is a feature of most patients with asthma. We have measured non-allergic bronchial reactivity to inhaled histamine and methacholine in thirteen asthmatic subjects before and after allergen inhalation in the laboratory. The allergen inhalation produced mild early asthmatic responses (19-40% FEV1 fall) in all thirteen, additional definite late asthmatic responses (17-29% FEV1 fall) in four, and equivocal late asthmatic responses (5-11% FEV1 fall) in five. Following allergen inhalation, non-allergic bronchial reactivity increased in seven for up to 7 days. The seven included all four with definite late asthmatic responses and three of the five with equivocal late asthmatic responses. We conclude that allergens make asthma worse, partly through non-allergic mechanisms, and that avoidance of allergens is important in reducing non-allergic bronchial hyper-reactivity.