Allergy-compatible symptoms among federated swimmers in Portugal: a cross-sectional study using the AQUA® questionnaire

Swimmers are chronically exposed to water disinfection by-products (commonly from chlorination) and to indoor air conditions that may aggravate allergic and respiratory symptoms. Evidence is robust for elite cohorts, but competitive swimmers outside Olympic settings remain understudied. We conducted a cross-sectional, anonymous online survey among Portuguese competitive swimmers, officially registered with the national federation, aged 16 years or older (April-May 2025). The validated Allergy Questionnaire for Athletes (AQUA^®; 21 items; positive ≥5 points) screened for allergy-compatible symptoms. Associations with demographics, training exposure, and pool environment were examined using descriptive statistics and bivariate tests (<i>α</i> = 0.05); exploratory logistic regression assessed independent predictors. Of 100 respondents, 95 valid questionnaires were analyzed. The prevalence of AQUA-positive screening was 81.1% (<i>n</i> = 77/95). Upper-airway complaints were most frequent (e.g., nasal obstruction 63.2%; rhinorrhea 61.1%), followed by cough 55.8% and ocular pruritus (51.6%). AQUA positivity was higher in women vs. men (88.7% vs. 71.4%, <i>p</i> = 0.036). Younger age (16-25 years) and ≥7 weekly training sessions were also associated with higher positivity (<i>p</i> = 0.011 and <i>p</i> = 0.012, respectively). A temperature gradient was evident (≤25 °C 50.0%; 25-27 °C 86.4%; 28-30 °C 83.3%; <i>p</i> = 0.013). Prior medical diagnosis of allergic disease and use of anti-allergic medication was strongly associated with AQUA positivity (<i>p</i> < 0.001). In multivariable analysis, female sex, younger age, ≥7 sessions/week, and pool water temperature >25 °C remained independent predictors. Allergy-compatible symptoms were common among competitive swimmers, with environmental and training-related correlations. Findings support routine symptom screening (AQUA) in clubs alongside attention to pool management (temperature, ventilation). Larger studies with clinical confirmation and objective environmental monitoring are warranted.