Mixing hydrogen peroxide and bleach can be extremely dangerous and should be avoided. When these two chemicals are mixed together, they react to form highly toxic gases that can cause serious health problems or even death.

Bleach is a strong oxidizing agent that is commonly used as a disinfectant and bleach. Hydrogen peroxide is also an oxidizing agent that is often used as a disinfectant, antiseptic, and bleaching agent. When these two chemicals are mixed together, they react to form oxygen gas and chlorine gas.
Chlorine gas is a powerful irritant that can cause respiratory problems, including coughing, wheezing, and shortness of breath. In high concentrations, chlorine gas can cause severe lung damage and even death. Oxygen gas is not toxic but can exacerbate fires and increase the risk of explosions.
The reaction between hydrogen peroxide and bleach can also produce other harmful byproducts, such as chloroform and hydrochloric acid. Chloroform is a toxic substance that can cause dizziness, nausea, and unconsciousness. Hydrochloric acid is a corrosive acid that can cause burns and damage to the respiratory system.
If someone accidentally mixes hydrogen peroxide and bleach, they should immediately leave the area and seek fresh air. They should also contact a poison control center or seek medical attention immediately, as exposure to the gases produced by this reaction can be extremely harmful.
To prevent accidental mixing of these chemicals, it is important to store them separately in clearly labeled containers and to never mix them intentionally. If using bleach or hydrogen peroxide for cleaning or disinfecting purposes, it is important to read and follow the instructions carefully and to never mix them with other chemicals.