Background: Refractory obsessive-compulsive disorder (OCD) represents a major clinical challenge. We describe the case of a 34-year-old male (F.R.C.) with severe OCD (baseline Y-BOCS = 24/40), childhood onset, eleven years of partial pharmacological response and documented hypersensitivity to multiple psychotropic drugs. The baseline qEEG (T0, 02/10/2025) was consistent with PANDAS with OCD comorbidity and emotional dysregulation. Intervention: An evidence-based naturopathic intervention was designed, personalised according to the T0 qEEG findings, and implemented over ~5 months (12/12/2025 – May 2026). The protocol comprised ten active compounds with published evidence in OCD, anxiety and/or neuroinflammation (inositol, saffron, DHA, Bacopa monnieri, two Traditional Chinese Medicine formulas, Streptococcus salivarius K12, Pelargonium spp., methylated B-complex, L-theanine), selected according to the individual neurophysiological profile and complementary to ongoing psychiatric treatment. Results: Y-BOCS decreased from 24/40 (severe OCD) to 20/40 (moderate OCD), exceeding the threshold for clinically significant response (≥3 points; Goodman et al., 1989). Clinically relevant improvements were observed in rumination (9→3/10), mood (3→7.5/10), mental clarity (3→7/10) and energy (3→7.5/10). The follow-up qEEG (T1, 28/05/2026, independent blinded centre) showed a pattern consistent with classic OCD without active diffuse neuroinflammatory substrate, qualitatively different from the slowed pattern at T0. Conclusion: This case illustrates the potential of an evidence-based naturopathic intervention, guided by qEEG, as an adjunct in refractory OCD. The diagnostic complexity — with possible overlap between OCD, PANDAS and unexplored indicators of atypical neurodevelopment — underscores the need for comprehensive assessments in this patient profile.