Effectiveness Demonstrated in Double-Blind RCT for Sudden Hearing Loss; Academic Verification of In-Body Explosion Risk from High-Concentration Hydrogen Inhalation

MiZ Co., Ltd. (Kamakura City, Kanagawa Prefecture) and the Graduate School of Medicine, Ehime University, demonstrated the effectiveness of low-concentration hydrogen inhalation for sudden hearing loss in the world's first double-blind randomized controlled trial (RCT) in November 2022 (published in Frontiers in Neuroscience). Subsequently, in January 2026, they published a paper academically verifying in-body explosion accidents caused by high-concentration hydrogen inhalers circulating in the market (published in The International Journal of Risk and Safety in Medicine).

This press release integrates these two research findings. Based on the scientific evidence that even low concentrations have a significant effect on severe sudden hearing loss and pose no explosion risk, MiZ Co., Ltd. advocates for a transition to "low-concentration hydrogen inhalation."

Background: Oxidative stress is also involved in sudden hearing loss

Idiopathic sudden hearing loss is a condition where hearing loss occurs suddenly without a clear cause, though it is thought to involve circulatory disturbances in the inner ear's microvasculature and oxidative stress from active oxygen. Standard treatment involves steroid administration, but many cases do not achieve sufficient recovery.

Hydrogen (H₂) is known to exert antioxidant and anti-inflammatory effects in vivo by scavenging highly reactive hydroxyl radicals. Animal experiments have reported inner ear protective effects from hydrogen inhalation, but clinical efficacy in humans had not been previously demonstrated.

Research Overview and Results

This study conducted a rigorous "double-blind randomized controlled trial" targeting 65 patients with sudden hearing loss across six medical institutions, including the Ehime University Hospital (Note 1).

[Methods]
Patients were randomly assigned to a "hydrogen inhalation group" (31 patients) and a "placebo (air) inhalation group" (34 patients). In addition to standard steroid treatment and prostaglandin E1 administration, they received 3% low-concentration hydrogen inhalation for one hour daily for six days.

[Results]
Three months after the start of treatment, hearing recovery was compared. The hydrogen inhalation group showed an average improvement of 32.7 dB (decibels), while the placebo group improved by 24.2 dB. Statistical analysis proved that the hydrogen inhalation group had significantly greater hearing recovery (P = 0.048). Furthermore, the probability of recovery (complete recovery) for severe sudden hearing loss was significantly higher in the hydrogen inhalation group compared to the air inhalation group (Figure 1).

[Safety]
No side effects were observed from hydrogen gas inhalation, confirming its high safety.

[Patent]
Our company and Ehime University School of Medicine have patented the research findings on the improvement of sudden hearing loss by hydrogen inhalation.

Figure 1: The cure rate of severe sudden hearing loss was significantly higher in the hydrogen inhalation group compared to the air inhalation group. Low-concentration hydrogen inhalation was revealed to have an improving effect on severe sudden hearing loss.

Dangers of High-Concentration Hydrogen Inhalers: "High Concentration" Increases Explosion Risk, "High Generation Rate" Magnifies Explosion Scale

Meanwhile, high-concentration hydrogen inhalers, the opposite of the low-concentration studied here, are prevalent in the market, and serious accidents have been reported.

A joint academic paper by MiZ Co., Ltd. and Keio University (published in The International Journal of Risk and Safety in Medicine) investigated serious accidents where hydrogen explosions occurred inside the body, such as in the nasal cavity or lungs, when using mixed gas with a hydrogen to oxygen ratio of 2:1 (Brown's gas: approx. 67% hydrogen) or 100% pure hydrogen. These incidents resulted in not only hearing loss but also complex facial fractures and massive hematemesis due to lung tissue burns due to the explosion's sound and shockwave (Note 2).

The nasal cavity is close to the brain, and the lungs are vital organs for respiration. Hydrogen explosions within these life-critical tissues can lead to more than just accidents, potentially exposing users to fatal risks. Some accidents reported to the Consumer Affairs Agency involving high-concentration hydrogen inhalers have been certified as "serious product accidents." Such high-concentration hydrogen inhalers should not be used in medical settings, let alone at home.

However, the market currently prioritizes specifications like "higher concentration" and "higher generation rate" over safety. High-concentration hydrogen only increases the risk of explosion, and a high generation rate only magnifies the scale of the explosion. It is a serious problem that devices intended for health purposes are designed to increase risks.

Ironically, attempting to inhale high-concentration hydrogen to improve sudden hearing loss could lead to irreversible hearing loss caused by the blast wave and noise of a hydrogen explosion, the exact opposite of the intended outcome.

On the other hand, the risk of explosion can be avoided if the hydrogen concentration is 10% or less. This joint research shows that even with 3% low-concentration hydrogen, there is an improvement effect on severe sudden hearing loss. Sufficient health benefits can be expected even with low concentrations that ensure safety.

The reason for this is that even at low concentrations, sufficient hydrogen molecules are supplied to eliminate hydroxyl radicals. This is also supported by calculations, demonstrating that the idea of "no effect without high concentration/high generation rate" lacks scientific basis (Figure 2).

Since hydroxyl radicals are constantly generated in the body as long as we breathe, it is most logical to inhale safe, low-concentration hydrogen for extended periods and at high frequency, free from the risk of explosion.

MiZ Co., Ltd. advocates for a transition to "low-concentration hydrogen inhalation," prioritizing safety (Note 3). Instead of pursuing high concentration and high generation rates, safe and sustainable hydrogen inhalation can become a new standard that benefits users.

Figure 2: Even with low-concentration hydrogen, a sufficient number of hydrogen molecules can be supplied to eliminate hydroxyl radicals generated within cells. Therefore, high concentration and high generation rate merely increase the risk and scale of hydrogen explosions and are completely meaningless.

Future Outlook

This research suggests that hydrogen inhalation may be an effective new therapeutic option for sudden hearing loss. Hydrogen's high diffusibility allows it to reach tissues with poor blood flow, such as the inner ear. MiZ Co., Ltd. and Ehime University will continue to promote the clinical application of low-concentration hydrogen inhalation, aiming to contribute to improving the Quality of Life (QOL) for many patients suffering from hearing loss.

Reference Information

(Note 1) Paper on Sudden Hearing Loss Improvement
English Title: A double-blinded, randomized controlled clinical trial of hydrogen inhalation therapy for idiopathic sudden sensorineural hearing loss
Japanese Title: 特発性突発性難聴に対する水素吸入療法の二重盲検ランダム化比較臨床試験
Journal: Frontiers in Neuroscience, 2022 Nov 24;16:1024634.
URL: https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2022.1024634/full

(Note 2) Paper on In-Body Hydrogen Explosions
English Title: Preventable In-Body Hydrogen Explosions from High-Concentration H₂ Inhalers in Japan —Switch to Safe, Low-Concentration Hydrogen Therapy—
Japanese Title: 日本における高濃度水素吸入器による人体内水素爆発とその防止策－低濃度水素療法への転換の必要性－
Journal: The International Journal of Risk and Safety in Medicine. 2026 Jan 5:9246479251414573.
Original URL: https://journals.sagepub.com/doi/10.1177/09246479251414573

(Note 3) Distribution of a Guidebook on Low-Concentration Hydrogen Inhalation
URL: https://e-miz.co.jp/pressrelease/pressrelease15.html

Inquiries Regarding Papers and Patents
MiZ Co., Ltd.
2-19-15 Ofuna, Kamakura City, Kanagawa Prefecture
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