A periodontics team at Guangxi Medical University pooled 13 randomised trials - 655 patients in all - that compared a standard deep clean with and without added ozone in people with periodontitis.

Eight of the trials used ozonated water and five used ozone gas.

Key findings: adding ozone produced a small but significant extra reduction in pocket depth and gum inflammation, with no increase in side effects. It made no significant difference to bleeding or plaque scores, and the effect on gum attachment fell just short of significance.

A dental college team in India gave 50 people with periodontitis the standard deep clean, then rinsed below the gumline with either freshly ozonated water or saline, and compared plaque, bleeding, pocket depth and gum attachment four weeks later.

Patients did not know which liquid they received.

Key findings: both groups improved, but the ozonated water group improved more on every measure - plaque and bleeding scores fell by about 28 percentage points against 17 to 18 with saline, and pockets shrank by just over 1 mm against 0.6 mm. No adverse effects were reported.

Researchers in Crimea randomly assigned 140 people with post-COVID asthenic syndrome - chronic fatigue, poor concentration, disturbed sleep and anxiety lasting months after infection - to a course of medication alone or medication plus ten daily infusions of ozonated saline, and compared oxidative stress markers and mental-status scores 30 days later.

Fifty healthy volunteers provided reference values.

Key findings: both groups improved, but the ozone group improved more on every measure. The lipid-damage marker malondialdehyde fell 69 per cent with ozone against 39 per cent without; antioxidant enzymes rose further; fatigue, insomnia, anxiety and cognition scores all improved more; and 94 per cent of the ozone group were rated free of illness against 63 per cent. No adverse events. No placebo and no blinding.

A Spanish university group sets out the case for testing ozone therapy in long COVID fatigue: why the condition overlaps with fibromyalgia and ME/CFS, how ozone is thought to act on the mechanisms they share, and what the handful of existing studies found.

This is a perspective article, not a trial - a short, referenced argument for a study the same team has since carried out.

Key points: long COVID, fibromyalgia and ME/CFS share fatigue, pain, cognitive symptoms, a viral trigger and systemic inflammation, so the authors argue they may respond to a shared approach. Three earlier ozone studies in post-COVID patients reported improvements in fatigue and function with no adverse effects. The authors propose an open pilot study of rectal insufflation.

Two long-standing ozone researchers pulled together every animal and human study that measured the body's antioxidant and oxidative-stress markers before and after low-dose ozone, across arthritis, diabetes, ageing, chemotherapy toxicity and ischaemia-reperfusion injury.

The question was whether controlled low-dose ozone shifts the balance between oxidative damage and the cell's own repair systems, and what that means for mitochondria.

Key findings: across the included studies, the antioxidant "repair" side rose by 21 to 140 per cent compared with untreated groups, with glutathione the central marker, while the damage marker malondialdehyde fell. Electron microscopy in animal models showed mitochondria kept their structure after ozone preconditioning. The authors describe low-dose ozone as a redox bioregulator.

A respiratory medicine team at Wuhan University randomly assigned 73 people with long COVID to receive either conventional care alone or conventional care plus major ozone autohaemotherapy, and compared symptoms, lung function, walking distance and blood markers before and after.

This is the only randomised controlled trial of ozone therapy in long COVID published so far.

Key findings: 71% of the ozone group had their symptom score at least halved, against 45% of the conventional-care group. Lung volume, walking distance, inflammatory and clotting markers and cellular immunity also improved more with ozone. No adverse effects were reported. The full paper is behind a paywall; this summary is written from the published abstract.

A Turkish rehabilitation specialist reviewed the records of 40 post-COVID patients who had completed ten sessions of major autohaemotherapy, comparing fatigue, anxiety, depression, sleep and quality-of-life scores before and after.

Nine in ten had fatigue as their main complaint.

Key findings: fatigue, anxiety and depression scores all fell significantly, sleep quality improved, and eight of nine quality-of-life domains improved. No adverse events were recorded. This is a retrospective review with no control group, so it shows what happened to these patients, not what caused it.

A Spanish university team gave 23 people with long COVID a 12-week course of rectal ozone insufflation and measured grip strength, quality of life and skin temperature at the start, at six weeks and at twelve.

This is the first published long COVID study to use rectal insufflation - the route most home users rely on - rather than autohaemotherapy.

Key findings: grip strength and both the physical and mental quality-of-life scores improved significantly by week six and held to week twelve. No adverse events of interest were recorded. There was no control group, so the authors describe the results as preliminary and hypothesis-generating.

A Spanish hospital team placed fine oxygen-sensing needle probes directly into the shin muscle of 23 patients and 3 volunteers, before and after systemic ozone therapy, to see whether tissue oxygen levels actually changed.

Ozone was given by autohaemotherapy on three alternate days over one week, with measurements before and after the first and third sessions.

Key findings: average oxygenation across everyone did not change significantly. But the proportion of severely oxygen-starved readings fell, the most poorly oxygenated muscles improved the most, and those tissues were still better oxygenated 48 hours after the second session.

An Italian study of 27 people with peripheral arterial disease measured how a single session of ozonised autohaemotherapy changed the flow properties of their blood - and used the same patients, given non-ozonised blood, as the control.

Blood viscosity, red cell filterability (a measure of how easily red cells squeeze through small pores), fibrinogen, haemoglobin's hold on oxygen and a marker of lipid peroxidation were measured before and 30 minutes after.

Key findings: after ozonised blood, viscosity and fibrinogen fell, red cell filterability rose and haemoglobin released oxygen more readily. Nothing changed when the same patients received the identical procedure without ozone. 2,3-DPG did not change significantly.

A randomised controlled trial of 101 people with type 2 diabetes and diabetic foot compared ozone - applied locally and by rectal insufflation - with topical and systemic antibiotics over 20 days.

The researchers tracked blood sugar control, the area and perimeter of the foot lesions, and blood markers of oxidative stress and blood-vessel damage.

Key findings: the ozone group showed better blood sugar control, normalised peroxide levels, activated superoxide dismutase, better lesion healing and fewer amputations than the antibiotic group, with no side effects reported. The full paper is paywalled, so figures are not reproduced here.

A randomised clinical study of 60 people with rheumatoid arthritis compared standard methotrexate treatment with the same treatment plus medical ozone given by rectal insufflation.

Disease activity, disability, anti-CCP antibodies, inflammatory blood markers and markers of oxidative stress were measured before and after 20 days of treatment.

Key findings: the group that added ozone showed reduced disease activity, lower anti-CCP levels, a stronger antioxidant system and less oxidative damage, while the methotrexate-only group showed only a tendency to improve. No side effects were observed. The full paper is paywalled, so effect sizes are not reproduced here.