Background: Strenuous exercise in sub-zero environments may cause airway injury and exercise-induced bronchoconstriction (EIB) (1). Atopic disposition is a risk factor for EIB development (2). However, it is currently unknown whether atopic disposition influences the acute respiratory responses to exercise in a sub-zero climate. Aim: To examine whether the respiratory responses to short- and long-duration exercise at -15⁰C differ between atopic and non-atopic subjects. Methods: Eighteen non-asthmatic, endurance-trained volunteers (males/females: 14/4, age: 29.4 ± 5.9 years old, maximal oxygen consumption (V̇O2max): 61.3 ± 8.7 ml/kg/min) were screened for atopy via the Allergy Questionnaire for Athletes (3) and completed two moderate-intensity (60% V̇O2max) environmental chamber running trials at -15⁰C lasting for 30 and 90 min in a randomized cross-over design. The study was conducted in accordance with the Declaration of Helsinki and was approved by the Swedish Ethical Review Authority. Dynamic spirometry (4) was performed at baseline and 15 and 55 min post-exercise to measure forced expiratory volume in 1 sec (FEV1). Venous blood samples collected pre-exercise and 10 and 65 min post-exercise were analysed for serum Clara cell secretory protein (CC16) using an enzyme-linked immunosorbent assay. A respiratory questionnaire (5) was administered before, immediately after and 20 min after exercise to examine the proportion of affirmative responses (‘YES’) to the occurrence of four symptoms (cough, wheezing, chest tightness and hypersecretion of mucus) associated with lower airways. To examine 2- and 3-way interaction effects on the relative change in FEV1 from baseline as well as the CC16 concentration, a 3-factor repeated measures ANOVA and a linear mixed-effects model were employed, respectively. A two-proportion z-test was performed to compare the symptom frequency between the two groups. Analyses entailing multiple comparisons were adjusted with the Benjamini-Hochberg method. Results: Atopy was identified in 10 subjects (56%, 7/3: men/women). There were no significant interaction effects for FEV1 or CC16 concentration (group x trial, FEV1: p = 0.35, CC16: p = 0.50; group x time, FEV1: p = 0.10, CC16: 0.10; group x trial x time, FEV1: p = 0.39, CC16: p = 0.51). Nevertheless, immediately after the 90-min trial, the onset of airway symptoms was significantly more frequent in atopic volunteers than their non-atopic peers (22.5% vs 0%, p < 0.01) with no intergroup differences observed 20 min post-trial. Atopic status did not affect the occurrence of the lower airway symptoms immediately after (10% in atopic vs 0% in non-atopic, p = 0.08) or 20 min after (5% in atopic vs 0% in non-atopic, p = 0.19) the 30-min trial. Conclusion: Atopy is not a major risk for bronchoconstriction when moderate-intensity exercise of either short or long duration is performed in a sub-zero climate by non-asthmatic subjects. Although the extent of bronchial epithelial damage did not differ between the two groups, atopic disposition may transiently elicit more lower airway symptoms after prolonged exercise.