Effects of sulphur thermal water inhalations in long-COVID syndrome: Spa-centred, double-blinded, randomised case–control pilot study

Background The long-COVID syndrome is characterised by a plethora of symptoms. Given its social and economic impact, many studies have stressed the urgency of proposing innovative strategies other than hospital settings. In this double-blinded, randomised, case–control trial, we investigate the effects of sulphur thermal water inhalations, rich in H2S, compared to distilled water inhalations on symptoms, inflammatory markers and nasal microbiome in long-COVID patients. Methods About 30 outpatients aged 18–75 with positive diagnosis for long-COVID were randomised in two groups undergoing 12 consecutive days of inhalations. The active group (STW) received sulphur thermal water inhalations whereas the placebo group received inhalations of sterile distilled non-pyrogenic water (SDW). Each participant was tested prior treatment at day 1 (T0), after the inhalations at day 14 (T1) and at 3 months follow-up (T2). At each time point, blood tests, nasal swabs for microbiome sampling, pulmonary functionality tests (PFTs) and pro-inflammatory marker measure were performed. Results The scores obtained in the administered tests (6MWT, Borg score and SGRQ) at T0 showed a significant variation in the STW group, at T1 and T2. Serum cytokine levels and other inflammatory biomarkers reported a statistically significant decrease. Some specific parameters of PFTs showed ameliorations in the STW group only. Changes in the STW nasopharyngeal microbiota composition were noticed, especially from T0 to T2. Conclusions Inhalations of sulphur thermal water exerted objective and subjective improvements on participants affected by long-COVID. Significant reduction of inflammatory markers, dyspnoea scores and quantitative and qualitative changes in the nasopharyngeal microbiome were also assessed.