Mixing bleach with ammonia produces toxic gases that are known as chloramines, according to the Washington State Department of Health. These gases cause a number of uncomfortable symptoms, including wheezing, irritation to the mucous membranes, pneumonia from fluid in the lungs, chest pain, nausea, watery eyes, trouble breathing and coughing.
Bleach is a highly reactive substance that also reacts with acids commonly found in household cleaners, the source explains, as well as with pool cleaners, oven cleaners, insecticides, hydrogen peroxide and other common household chemicals. Combining bleach with acid produces chlorine gas, which can cause issues that include respiratory difficulty and burns. Exposure to high levels of chlorine can be lethal. The Washington State Department of Health warns against mixing bleach with other substances for this reason. Anyone exposed to toxic fumes after mixing bleach and other chemicals should contact a health care professional immediately.