PurposeTo assess whether preoperative C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), immunoglobulin E (IgE), and blood eosinophil percentage (EOS) can predict need for steroid irrigations after FESS. Materials and methodsAdult patients at BIDMC from inception until September 8, 2023 with chronic rhinosinusitis with nasal polyps who underwent FESS and had preoperative CRP (n = 129), ESR (n = 79), IgE (n = 107), or EOS (n = 125) were included. Labs were divided into normal (CRP: 0–5.0 mg/L; ESR: 0-15 mm/h; IgE: 150-300Ul/mL; EOS: 1–7 %) and high groups (CRP: >5.0 mg/L; ESR: >15 mm/h; IgE: >300Ul/mL; EOS: >7 %). The primary outcome was need for intranasal steroid irrigations after FESS (≤4 weeks, 4–12 weeks, 12–26 weeks, 26–52 weeks, 1–3 years, 3–5 years, and > 5 years). Receiver operating characteristic curves were created to determine thresholds for predicting postoperative steroid irrigations. ResultsElevated IgE required intranasal steroid irrigation at 1–3 years (normal 34 %, high 62 %, p = 0.02), 3–5 years (normal 24 %, high 48 %, p = 0.04), and > 5 years (normal 19 %, high 43 %, p = 0.02). Elevated EOS required intranasal steroid irrigation at 26–52 weeks (normal 7 %, high 25 %, p = 0.009) and > 5 years (normal 19 %, high 46 %, p = 0.005). The area under the curve for IgE at 1–3 years was 0.696 (95 % CI: 0.597–0.795) with cutoff at 144–148 Ul/mL. CRP and ESR were not predictive of postoperative intranasal steroid treatment. ConclusionsElevated IgE and EOS (but not CRP or ESR) may predict need for intranasal steroid treatment after FESS.