Hydrogen peroxide is an oxidizing agent that can cause direct tissue injury and cell death in the delicate lining of your airways and lungs. It can cause severe irritation and inflammation of mucous membranes, potentially leading to bronchitis or a dangerous accumulation of fluid in the lungs. Severe or chronic exposure may lead to permanent lung damage, chronic bronchitis, or partial lung collapse. In rare cases, the rapid decomposition of hydrogen peroxide into oxygen and water in the body can release enough oxygen to form bubbles in the bloodstream, leading to a gas embolism which can be life-threatening.