BACKGROUND: Pollen allergy may influence irritable bowel syndrome (IBS) symptoms; however, available data are scant. AIMS: This study aims to assess symptom variability in atopic IBS patients. METHODS: We retrospectively analysed consecutive adult IBS patients evaluated between 2021 and 2024. Patients from the overall IBS cohort and the IBS-diarrhoea (IBS-D) subgroup were classified according to their sensitisation into grass-positive, house dust mite (HDM)-positive, or unsensitised. Symptom burden was assessed using the gastrointestinal symptom rating scale (GSRS) and a visual analogue scale for abdominal pain/distension, both outside the season period (T0) and during the pollination season (T1). RESULTS: A total of 61 IBS patients were recruited (median age 34 years, IQR 25-50, F:M ratio 3.6:1), including 38 patients (62.8%) with IBS-D (median age 30 years, IQR 28-47, F:M ratio 2.8:1). Atopy was common in the IBS-D subgroup, particularly with respiratory manifestations. The mean GSRS significantly ( < 0.01) increased at T1 (variance of 3.4 points) only in grass-sensitised patients as opposed to those sensitised to HDM or unsensitised ones; this effect was present only in the IBS-D subgroup, while no significant variation was observed in the overall cohort. CONCLUSIONS: Pollination season influences symptoms in IBS-D patients sensitised to seasonal allergens.